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Evaluating selection at intermediate scales within genes provides robust identification of genes under positive selection in M. tuberculosis clinical isolates.

Multiple studies have reported genes in the M. tuberculosis (Mtb) genome that are under diversifying selection, based on genetic variants among Mtb clinical isolates. These might reflect adaptions to selection pressures associated with modern clinical treatment of TB. Many, but not all, of these genes under selection are related to drug resistance. Most of these studies have evaluated selection at the gene-level. However, positive selection can be evaluated on different scales, including individual sites (codons) and local regions within an ORF. In this paper, we use GenomegaMap, a Bayesian method for calculating selection, to evaluate selection of genes in the Mtb genome at all three levels. We present evidence that the intermediate analysis (windows of codons) yields the most credible list of candidate genes under selection (excluding PPE and PE_PGRS genes, which are predicted less reliably due to frequent sequencing errors). A further advantage of this approach is that it identifies specific regions within proteins that are under selective pressure, which is useful for structural and functional interpretation. In an analysis of two separate collections of Mtb clinical isolates (from Moldova; and a globally-representative set), we observed 53 and 173 significant genes under selection, with 36% overlap. The lists of genes under selection include many drug-resistance genes, as well as other genes that have previously been reported to be under selection (resR, phoR). The specific regions under selection identified within drug-resistance genes are shown to correspond to protein structural features known to be involved in resistance, supporting accuracy of the method. Positive selection in several ESX-1-related genes was also observed, suggesting adaptation to immune pressure.

adaptation

Diversification of Cellulose Synthase (CESA) Genes in Mosses Suggests Both Ancient and Recent Gene duplications.

Cellulose is an important polysaccharide that constitutes all plant cell walls, giving them strength and stability. The plant cellulose synthase (CESA) gene family, which encodes the catalytic subunits of cellulose synthesis complexes (CSCs), has diversified independently in several plant lineages, providing an interesting model for understanding selection for gene duplication. Here we quantified the presence of CESA genes across mosses to understand how the process of gene family diversification occurred in this group and how it parallels diversification in other groups. We first examined the CESA gene family in eight species of mosses across seven families for which whole genome assemblies were available. We then identified CESA genes from additional species, for which only short-read sequence data was available, by using BLAST searches and targeted gene assemblies. We validated this approach by comparing the assembled paralogs from the short-read data to the genes identified from whole genome assemblies in the eight reference species. This approach allowed us to identify paralogs directly from short-read data and greatly expand our sample set. Results from the combined empirical data support the hypothesis that CESA genes diversified within the moss lineage at least as early as the mesozoic period, during or possibly even prior to the onset of moss diversification, but also continue to diversify within modern species. In addition, we found evidence for purifying selection as the dominant force shaping these genes and observed that different lineages experienced different levels of evolutionary constraint. Lastly, our approach to assemble paralogs has the potential to allow researchers to improve analyses of gene duplication events.

Physcomitrium patens

The ovalbumin gene: alleles created by mutations in the intervening sequences of the natural gene.

Two allelic forms of the natural chicken ovalbumin gene have been independently cloned. These alleles differ from each other by an Eco RI restriction cleavage site in one of the seven intervening sequences within the natural ovalbumin gene. Restriction endonuclease mapping and sequence analyses of these cloned genotypic alleles have shown identical sequence organization and molecular structures of the interspersed structural and intervening sequences except for the particular Eco RI cleavage site. Sequencing data of the cloned DNA suggest that this Eco RI site may be created or eliminated by a single base mutation in the intervening sequence of the ovalbumin gene. The occurrence of apparent homozygous and heterozygous allelic forms of the ovalbumin gene in individual hens and roosters within the same breed has been observed. 10 and 40% of the chickens examined are homozygous for the ovalbumin gene with and without the extra Eco RI site, respectively, while 50% of them are heterozygous. Further analysis of individual chicken DNA cleaved by restriction endonuclease Hae III has revealed that there may be a series of such mutational variations within the ovalbumin gene. We have identified two Hae III cleavage sites that do not occur in all of the chickens, thus giving rise to several additional allelic variations of the ovalbumin gene. At least one of these Hae III sites is situated in the intervening sequence of the ovalbumin gene, and its lcoation has been mapped. Such allelic variations must be taken into consideration when determining eucaryotic gene structure by restriction mapping of the genomic DNA. Furthermore, this type of mutation within the intervening sequences of an eucaryotic gene has no known phenotypic manifestation. It represents an extrastructural silent mutation that must be taken account of in studies to estimate the rates of eucaryotic gene sequence divergence during evolution.

Alleles

Isolation of the chicken beta-globin gene and a linked embryonic beta-like globin gene from a chicken DNA recombinant library.

A library of random chicken DNA fragments, 15-22 kb long, has been prepared in the vector lambda Charon 4A. This library was screened with combined adult and embryonic globin cDNA, and several independent globin gene-containing recombinants were isolated. One of these recombinants, lambda Chicken beta-globin 1 (lambda C beta G1), contains the adult chicken beta-globin gene and a closely linked embryonic beta-like globin gene. Both genes are transcribed in the same direction with the adult gene located 5' to the embryonic gene. Electron microscopic visualization of R loop structures generated by hybridization of globin RNA to lambda C beta G1 demonstrates that both globin genes contain major intervening sequences about 800 bp long, similar to those present in mammalian beta-globin genes. The adult beta-globin gene also contains a minor (approximately 100 bp long) intervening sequence analogous to the one observed in mammalian beta-globin genes. Restriction enzyme analysis of the adult beta-globin gene on lambda C beta G1 is consistent with the hypothesis that its two intervening sequences occur in the same positions with respect to the beta-globin amino acid sequence as do the corresponding mammalian intervening sequences.

Animals

Hemoglobin switching in sheep: only the gamma gene is in the active conformation in fetal liver but all the beta and gamma genes are in the active conformation in bone marrow.

Differential expression of the closely linked gamma, beta(A) (or beta(B)), and beta(C) globin genes in sheep results in the production of fetal hemoglobin (Hb F, alpha(2)gamma(2)) during gestation and the adult hemoglobins (Hb A, alpha(2)beta(2) (A), and Hb B, alpha(2)beta(2) (B)) after birth. Erythropoietic stress in certain animals leads to production of Hb C (alpha(2)beta(2) (C)). The molecular mechanism of differential expression of these genes in nuclei of fetal and adult erythroid cells has been investigated by analysis of their susceptibility to digestion by DNase I (genes that are in the conformation associated with active transcription are sensitive to this nuclease). The concentration of globin gene sequences in DNA from control and DNase I-digested nuclei was determined by annealing to synthetic DNAs and analogous cDNA probes derived from recombinant plasmids containing one of the sheep globin genes. In nuclei from sheep fetal liver erythroid cells, the gamma genes but not the beta genes were digested by DNase I; the gamma locus was open but the beta(A) or beta(C) loci was closed, consistent with synthesis of only Hb F by these cells. DNase I digestion of nuclei from bone marrow of anemic sheep making only Hb C or Hb B resulted in equivalent digestion of the beta and gamma gene sequences, although gamma mRNA was not detected in these cells. Digestion by DNase I did not decrease the globin gene sequence concentration in residual DNA of spleen nuclei. As a further control, DNA from digested bone marrow and spleen nuclei were shown to anneal equally well to a cDNA prepared from liver polysomal mRNA. Differential expression of the gamma and beta globin genes in sheep fetal erythroid cell appears to be based on differences in chromatin structure. The gamma globin gene remains in the active conformation in adult erythroid cells; failure of gamma mRNA to accumulate in these cells probably reflects transcriptional or post-transcriptional regulation.

Animals

Anatomy of the RNA and gene products of MC29 and MH2, two defective avian tumor viruses causing acute leukemia and carcinoma: evidence for a new class of transforming genes.

The RNA species of the defective avian acute leukemia virus MC29 and of the defective avian carcinoma virus MH2 and of their helper viruses were analyzed using gel electrophoresis, fingerprinting of RNase T1-resistant oligonucleotides, RNA-cDNA hybridization and in vitro translation. A28S RNA species, of 5700 nucleotides, was identified as MC29- or MH2-specific. MC29 RNA shared 4 out of about 17 and MH2 RNA at least 1 out of 16 T1-oligonucleotides with several other avain tumor virus RNAs. In addition MC29 and MH2 RNAs shared 2 oligonucleotides which were not found in any other viral RNA tested. 60% of each 28S RNA could be hybridized by DNA complementary to other avian tumor virus RNAs (group-specific) but 40% could only be hybridized by homologous cDNA (specific). Src gene-related sequences of Rous sarcoma virus were not found in MC29 or MH2 RNA. The specific and group-specific sequences of MC29, defined in terms of their T1-oligonucleotides, were located on a map of all T1-oligonucleotides of viral RNA. Specific sequences mapped between 0,4 and 0,7 map units from the 3'poly(A) end and group-specific sequences mapped between 0 and 0,4 and 0,7 and 1 map units. The MC29-specific RNA segment was represented by 6 oligonucleotides, two of which were those shared only by MC29 and MH2 RNAs. In vitro translation of MC29 RNA generated a major 120 000 dalton protein and minor 56 000 and 37 000 dalton proteins. The 120 000 dalton protein shared sequences with the proteins of the avian tumor viral gag gene, which maps at the 5' end of independently replicating viruses. Since a gag gene-related oligonucleotide was also found near the 5' end of MC29 RNA, we propose that the 120 000 MC29 protein was translated from the 5' 60% of MC29 RNA. It would then include sequences of the defective gag gene as well as MC29-specific sequences. Since both MC29 and MH2 lack the src (sarcoma) gene of Rous sarcoma virusk it is concluded that they contain a distinct class of transforming (onc) genes. We propose that the specific sequences of MC29 and MH2 represent all, or part of, their onc genes because the onc genes of MC29 and MH2 are specific and represent the only known genetic function of these viruses. If this proposal is correct, the onc genes of MC29 and MH2 would be related, because the specific RNA sequence of MC29 shares 2 of 6 oligonucleotides with MH2. It would also follow that the 120 000 dalton MC29 protein is a probable onc gene product, because it is translated from MC29-specific (and group-specific) sequences and because both MC29- and MH2-transformed cells contain specific 120 000 and 100 000 dalton proteins, respectively.

Avian Leukosis Virus

Gene behaviors-based network enrichment analysis and its application to reveal immune disease pathways enriched with COVID-19 severity-specific gene networks.

MOTIVATION: Gene network analysis is essential for understanding the complex mechanisms underlying diseases, which often involve disruptions in molecular networks rather than individual genes. Despite the availability of large-scale omics datasets and computational tools for gene network analysis, interpretation of the biological relevance of these extensive networks remains challenging. RESULTS: We propose a novel computational strategy, gene behaviors-based network enrichment analysis, which systematically identifies functional pathways enriched in phenotype-specific gene networks. Our novel method incorporates comprehensive network characteristics, i.e. gene expression levels, edge strengths, and structural patterns of edges, to rank genes based on activity and assess pathway enrichment, effectively identifying functional pathways enriched within these networks. Through simulation studies, our strategy demonstrated superior performance compared with that of existing methods in identifying enriched pathways. We applied this strategy to whole-blood RNA-seq data from 1102 COVID-19 samples provided by the Japan COVID-19 Task Force. The analysis revealed immune disease pathways enriched with COVID-19 severity-specific gene networks, including "Systemic lupus erythematosus" in asymptomatic and severe samples and "Inflammatory bowel disease," "Primary immunodeficiency," and "Rheumatoid arthritis" in mild samples. Key biomarkers of COVID-19, such as CXCL8, S100A9, and HLA class I genes, have been identified as critical hub genes and the main players within these networks. AVAILABILITY AND IMPLEMENTATION: Code is available in Figshare (https://doi.org/10.6084/m9.figshare.29093648.v3).

COVID-19

Coexpression of neighboring genes in Caenorhabditis elegans is mostly due to operons and duplicate genes.

In many eukaryotic species, gene order is not random. In humans, flies, and yeast, there is clustering of coexpressed genes that cannot be explained as a trivial consequence of tandem duplication. In the worm genome this is taken a step further with many genes being organized into operons. Here we analyze the relationship between gene location and expression in Caenorhabditis elegans and find evidence for at least three different processes resulting in local expression similarity. Not surprisingly, the strongest effect comes from genes organized in operons. However, coexpression within operons is not perfect, and is influenced by some distance-dependent regulation. Beyond operons, there is a relationship between physical distance, expression similarity, and sequence similarity, acting over several megabases. This is consistent with a model of tandem duplicate genes diverging over time in sequence and expression pattern, while moving apart owing to chromosomal rearrangements. However, at a very local level, nonduplicate genes on opposite strands (hence not in operons) show similar expression patterns. This suggests that such genes may share regulatory elements or be regulated at the level of chromatin structure. The central importance of tandem duplicate genes in these patterns renders the worm genome different from both yeast and human.

Animals

Suppression of gene 49 mutations of bacteriophage T4 by a second mutation in gene X: structure of pseudorevertant DNA.

Mutations in gene 49 of bacteriophage T4 were suppressed by a second mutation in gene X. Mapping studies located gene X between genes 41 and 42. Complementation results indicated that mutations in FdsA gene (a suppressor of gene 49 mutants) were in gene X. The intracellular pseudorevertant DNA was examined for unusual properties which could explain its successful encapsidation. After the in vivo inactivation of a temperature-sensitive gene 32 (DNA unwinding) protein, the intracellular pseudorevertant DNA was converted into DNA pieces of approximately genome size. A similar conversion was observed after in vitro digestion of pseudorevertant DNA with single-strand-specific S1 endonuclease. Appreciable quantities of oligomeric intermediates were not produced during this conversion process. These data indicate that pseudorevertant DNA contains sizable single-stranded gaps and has a conformation similar to that of wild-type DNA. The results further suggest that the suppression of gene 49 mutant abnormal DNA phenotype and the encapsidation defect by a second mutation in gene X is associated with the formation of sizable single-stranded gaps. These studies raise the possibility that single-stranded gaps may be involved directly in the DNA encapsidation process, or may act indirectly as a consequence of their effect on the organization of intracellular DNA.

Coliphages

Nonallelic histone gene clusters of individual sea urchins (Lytechinus pictus): polarity and gene organization.

We have analyzed the histone genes from the sea urchin Lytechinus pictus. Examination of native DNA from individuals reveals four major Eco RI restriction endonuclease histone gene DNA fragments which have been labeled A (6.0 kb), B (4.1 kb), C (3.1kb) and D (1.2 kb). The fragments A, B and C have been cloned into E. coli plasmids (pLpA, pLpB and pLpC). These histone gene fragments display length and sequence heterogeneity in different individuals. The plasmid pLpA contains the coding regions for H1, H4, H2B and H3 histones, and we determined that the DNA fragment D is tandem to A in native DNA and that it contains the H2A gene. The plasmids pLpB and pLpC contain the histone genes H2A-H1-H4 and H2B-H3, respectively, and together contain the sequences for the five major histones. Restriction analysis of native L. pictus DNA reveals that B and C are tandem to each other but not intermingled with the A--D-type repeat units, and are thus in separate clusters with a repeat length of 7.2 kb. Since the two cluster types do not segregate, they are not alleles. Hybridization of histone mRNA to exonuclease III-digested linear DNA demonstrated an identical polarity of the histone genes in the A--D- and B--C-type repeat units. This result revealed that the L. pictus histone genes have a polarity which is the same as other sea urchin histone genes examined to date--that is, 3' H1-H4-H2B-H3-H2A 5'. Restriction endonuclease cleavage patterns of the cloned segments indicate that considerable sequence heterogeneity exists between the two types of histone gene repeat units.

Animals

Differential gene expression study in whole blood identifies candidate genes for psychosis in African American individuals.

Genome-wide association has identified regions of the genome that mediate risk for psychosis. It is possible that variants in these regions confer risk by altering gene expression. This work has predominantly been conducted in individuals of European descent and has focused narrowly on schizophrenia rather than psychosis as a syndrome. In the present study we investigated alterations in gene expression in African American individuals with a range of psychotic diagnoses to increase understanding of the etiology in an underserved population. We performed RNA-seq in whole bloody to survey the transcriptome in 126 patients with a psychosis-spectrum disorder and 217 healthy controls and applied differential gene expression analyses across the genome while controlling for age, sex, population stratification and batch. We found 18 differentially expressed genes (DEGs), some of the locations of the corresponding genes overlap with previously implicated regions for psychosis, but many of which were novel associations. Enrichment analysis of nominally significant genes (p&#xa0;<&#xa0;0.05) revealed overrepresentation of biological processes relating to platelet, immune and cellular function, and sensory perception. Weighted gene co-expression network analysis, applied to identify modules of co-expressed genes associated with psychosis, revealed 10 modules, one of which was significantly associated with psychosis. This module was significantly enriched for DEGs, and for platelet function. These results support the potential role of immune function in the etiology of psychosis, identify novel candidate gene expression phenotypes that correspond to both established and new genomic regions, in individuals of African American ancestry.

Humans

Recent gene duplication and structural remodeling drive rapid lineage-specific gene family evolution in plants.

Gene duplication promotes the generation of novel gene functions and trait diversity across species. Here, we present DupHIST, a computational pipeline that reconstructs the hierarchical timing of gene duplications by integrating maximum likelihood (ML)-based phylogeny with substitution-derived timing via statistical smoothing. Applied to over 4.5 million genes from 114 plant genomes, we successfully inferred duplication histories across nearly 130,000 orthogroups. This large-scale analysis showed that 53.0% of genes arose from recent, lineage-specific duplications, with high concentrations in particular multi-copy families. Among these, NLR, C48, and P450 families exemplified how recently duplicated genes undergo rapid stepwise structural remodeling. This process was primarily driven by small-scale mutations, including insertions, deletions, and frameshifts, that rapidly accumulated shortly after duplication. By resolving the precise duplication order, we reconstructed these architectural changes, thereby enabling both the inference of putative ancestral structures and the exploration of functional diversification arising from structural remodeling. Structure-based clustering further uncovered that recently duplicated, uncharacterized genes retain core domain structures resembling known functional proteins even across phylogenetically distant species lacking sequence homology. Our findings reveal that recent gene duplications and subsequent structural remodeling represent a widespread and lineage-specific force driving rapid diversification of gene families in plants.

Gene duplication history

The msf gene causes condition-specific shifts in global gene expression in Haemophilus influenzae.

UNLABELLED: Haemophilus influenzae is a diverse human-restricted bacterium that normally colonizes the healthy nasopharynx but also causes common infections. Comparisons of clinical isolate genomes previously identified a gene, msf, that contained Sel1-like repeats that were associated with clinical disease. Mutant analysis had further found that msf improved survival in macrophages and increased systemic infection in an animal model. However, the role of msf in other conditions and its molecular function remain unknown. To identify protein-protein interactions with Msf, a yeast two-hybrid screen against an H. influenzae prey library was conducted, which found potential interactions with lipoprotein exporter protein LolD and an autotransporter adhesin Hap. To identify effects of msf on gene expression, we compared wild-type and mutant strains grown in multiple culture conditions by RNA-seq. The results indicate that msf modulates global gene expression in a condition-dependent manner, exerting an especially strong influence in starved surface-attached biofilm cells. The few consistent changes in mutants' planktonic exponential and stationary phases included decreased expression of two paralogous autotransporter adhesins. By contrast, mutant cells in starved surface-attached biofilms had dramatic changes in expression, including upregulation of protein translation and downregulation of alternative carbon metabolism. However, assays of 24 hour biofilm phenotypes found only subtle gene expression changes. Together, the results point to a speculative model of Msf functioning as an envelope-associated chaperone whose presence affects the relative expression of proteins at the outer membrane. IMPORTANCE: Comparing genomes from different clinical isolates of the same pathogenic bacterial species has identified genes associated with virulence, but many of these are understudied or have no known function. The msf gene was previously implicated as a virulence factor in Haemophilus influenzae, a common cause of mucosal diseases including middle-ear and chronic lung infections. This study finds that the msf gene causes condition-specific changes in gene expression, with especially dramatic changes in starved surface-attached biofilm cells. Along with identification of putative protein-protein interaction partners, the results provide new clues as to the molecular and cellular function of Msf, potentially as an envelope-associated chaperone involved in membrane protein trafficking. Understanding how virulence-associated genes like msf modulate bacterial responses to the environment may help explain why some bacterial strains remain harmless colonizers while others become pathogens.

Haemophilus influenzae

Bacteriophage phiX174: gene A overlaps gene B.

The map position of several phiX174 mutations in the genes A and B was determined by marker rescue with DNA fragments produced by the restriction enzymes Hha I, HindII, Hae III, and Alu I. All the gene B mutants were found to be located within gene A. Genetic complementation and analysis of phage-specific protein synthesis show that, under restrictive conditions, nonsense mutants in gene A do not block the synthesis and activity of the B protein and nonsense mutants in gene B do not affect the gene A function. The map position of the COOH-terminal end of gene A was determined using an amber mutant that synthesizes slightly shortened A and A proteins. It is concluded from these experiments that gene A overlaps gene B completely (or almost completely) and that the overlap region can be translated in two ways with different reading frames: one frame for the synthesis of the A and A proteins and another for the synthesis of the B protein.

Coliphages

"Host shutoff" function of bacteriophage T7: involvement of T7 gene 2 and gene 0.7 in the inactivation of Escherichia coli RNA polymerase.

The "host shutoff" function of bacteriophage T7 involves an inactivation of the host Escherichia coli RNA polymerase by an inhibitor protein bound to the enzyme. When this inhibitor protein, termed I protein, was removed from the inactive RNA polymerase complex prepared from T7-infected cells by glycerol gradient centrifugation in the presence of 1 M KCl, the enzyme recovered its activity equivalent to about 70 to 80% of the activity of the enzyme from uninfected cells. Analysis of the activity of E. coli RNA polymerase from E. coli cells infected with various T7 mutant phages indicated that the T7 gene 2 codes for the inhibitor I protein. The activity of E. coli RNA polymerase from gene 2 mutant phage-infected cells, which was about 70% of that from uninfected cells, did not increase after glycerol gradient centrifugation in the presence of 1 M KCl, indicating that the salt-removable inhibitor was not present with the enzyme. It was found that the reduction in E. coli RNA polymerase activity in cells infected with T7(+) or gene 2 mutant phage, i.e., about 70% of the activity of the enzyme compared to that from uninfected cells after glycerol gradient centrifugation in the presence of 1 M KCl, results from the function of T7 gene 0.7. E. coli RNA polymerase from gene 0.7 mutant phage-infected cells was inactive but recovered a full activity equivalent to that from uninfected cells after removal of the inhibitor I protein with 1 M KCl. E. coli RNA polymerase from the cells infected with newly constructed mutant phages having mutations in both gene 2 and gene 0.7 retained the full activity equivalent to that from uninfected cells with or without treatment of the enzyme with 1 M KCl. From these results, we conclude that both gene 2 and gene 0.7 of T7 are involved in accomplishing complete shutoff of the host E. coli RNA polymerase activity in T7 infection.

Coliphages

New late gene, dar, involved in the replication of bacteriophage T4 DNA. II. Overproduction of DNA binding protein (gene 32 protein) and further characterization.

We have previously shown that the arrested DNA synthesis of mutant defective in T4 phage gene 59 can be reversed by a mutation in dar. In this paper, we have examined the effect of the dar mutation on the kinetics of gene 32 protein (DNA binding protein) synthesis, DNA packaging, progeny formation, and several other porcesses. Several lines of evidence are presented showing that the regulation of synthesis of gene 32 protein is abnormal in dar 1-infected cells. In these cells, gene 32 protein, an early protein, is also expressed late in the infectious cycle. Our data also indicate that the packaging og DNA into T4 phage heads is delayed in dar mutant-infected cells, and this in turn results in a 6- to 8-min delay in intracellular progeny formation, although the synthesis of late proteins appears to be normal, as shown by gel electrophoresis. We have also studied the phenotypes of the double mutant dar-amC5 (gene 59). The increased sensitivity to hydroxyurea caused by a mutation in the dar gene can be alleviated by a second mutation in gene 59, but an increased sensitivity to UV irradiation caused by a mutation in gene 59 cannot be alleviated by a second mutation in the dar gene. Therefore, the double mutant still exhibits abnormalities in the repair of UV lesions.

Coliphages

Gene regulation technologies for gene and cell therapy.

Gene therapy stands at the forefront of medical innovation, offering unique potential to treat the underlying causes of genetic disorders and broadly enable regenerative medicine. However, unregulated production of therapeutic genes can lead to decreased clinical utility due to various complications. Thus, many technologies for controlled gene expression are under development, including regulated transgenes, modulation of endogenous genes to leverage native biological regulation, mapping and repurposing of transcriptional regulatory networks, and engineered systems that dynamically react to cell state changes. Transformative therapies enabled by advances in tissue-specific promoters, inducible systems, and targeted delivery have already entered clinical testing and demonstrated significantly improved specificity and efficacy. This review highlights next-generation technologies under development to expand the reach of gene therapies by enabling precise modulation of gene expression. These technologies, including epigenome editing, antisense oligonucleotides, RNA editing, transcription factor-mediated reprogramming, and synthetic genetic circuits, have the potential to provide powerful control over cellular functions. Despite these remarkable achievements, challenges remain in optimizing delivery, minimizing off-target effects, and addressing regulatory hurdles. However, the ongoing integration of biological insights with engineering innovations promises to expand the potential for gene therapy, offering hope for treating not only rare genetic disorders but also complex multifactorial diseases.

Humans

A duplicated female pathway gene figla-like evolves as the male sex-determining gene in tilapia.

As the largest group of vertebrates, fish exhibit frequent turnover of sex-determining (SD) genes. Here, we assemble a chromosome-level YY red tilapia genome and identify figla-like (figlal) as the SD gene on tilapia linkage group (LG) 1. Integrative phylogenetic and genomic evidence suggests that figlal originated from a tilapia-specific duplication and transposition of the ancestral bHLH family gene figla from LG12 to LG1. Fluorescence in situ hybridization reveals expression divergence between figla and figlal, with figla expressed in female oocytes and figlal expressed in male gonadal somatic cells during early gonadal differentiation. The shift in expression after duplication might be driven by the insertion of cis-regulatory elements mediated by transposable elements. Knockout of figlal in XY fish results in male-to-female sex reversal as indicated by ovarian morphology, down-regulation of the male pathway gene dmrt1, and up-regulation of the female pathway gene cyp19a1a in the gonads. In contrast, overexpression of figlal in XX fish induces female-to-male sex reversal. These findings implicate figlal as an SD gene on tilapia LG1 and reveal the history of a unique evolutionary innovation in which a female oocyte gene evolved into a male SD gene via duplication, transposition, and cis-regulatory rewiring.

Animals