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Evolutionary Conservation and Reproductive Expression of ABC Transporter Genes in Two Sphenomorphus Skinks.

ATP-binding cassette (ABC) transporters represent one of the largest membrane protein superfamilies in vertebrates, playing essential roles in translocating diverse substrates across membranes. However, knowledge of ABC transporter genes in reptiles remains limited. In this study, we conducted a comprehensive genome-wide identification and characterization of the ABC gene family in oviparous Sphenomorphus incognitus and viviparous Sphenomorphus indicus. A total of 45 ABC genes were identified in each species and classified into seven subfamilies (ABCA-ABCG). Comparative and phylogenetic analyses revealed a generally conserved gene repertoire, with limited duplication events observed mainly in the ABCA and ABCG subfamilies, whereas other subfamilies (e.g., ABCE, ABCF, and ABCD) remained highly conserved. Interestingly, a lineage-specific duplication of ABCC2 was identified in lizards. Oviductal expression profiling revealed distinct temporal patterns of ABC gene expression across reproductive stages. Several genes, including ABCG1, ABCC3, and ABCD4, exhibited conserved expression trajectories across both species, suggesting shared transcriptional regulation. In contrast, ABCA1, ABCB1, and ABCG2 showed species-specific expression patterns, indicating regulatory divergence between the two lizard species. Overall, ABC gene expression was more dynamic in S. incognitus than in S. indicus. In summary, although the ABC transporter family is structurally conserved, it exhibits lineage-specific evolutionary changes and divergent transcriptional regulation in lizard oviducts. This study provides a foundation for understanding the diversity and regulation of ABC transporter genes in reptiles.

Animals

Basic chromosomal proteins in lower eukaryotes: relevance to the evolution and function of histones.

The occurence of the basic chromosomal proteins in lower eukaryotes provides a useful approach to the study of histone evolution and function in higher eukaryotes. The histones of higher plants and animals are very similar and some are nearly identical, suggesting a high degree of evolutionary conservation within this group of proteins. However, a literature survey reveals that in the lower eukaryotes the histone situation is quite variable. The ciliates, and the true and cellular slime molds possess basic chromosomal proteins that are very similar to the histones of higher plants and animals. Various other lower eukaryotes possess basic chromosomal proteins that resemble at least some of the major histone fractions, and some microorganisms possess basic chromosomal proteins that bear little or no relationship to higher plant and animal histones. Since histones play a major role in the control of gene expression and the maintenance of chromosome structure in higher organisms, the evolution of these proteins represents a major change in the packaging of DNA and the mode of regulating gene expression in eukaryotes.

Animals

Exploring the genetics of social behaviour in C. calcarata.

Studies investigating social evolution often focus on species that are obligately eusocial, where presumably all of the adaptive genetic changes associated with sociality have already been completed. To fully understand eusociality, we must study species with facultative social behaviour. The small carpenter bee Ceratina calcarata is an ideal model for studying the genetics and molecular biology of eusocial evolution as it can exhibit both subsocial behaviour with parental care and social behaviour facilitated by the altruistic dwarf eldest daughter. Here, we sequenced the genomes of subsocial and social C. calcarata to identify mutations and genes associated with social behaviour and used these data to test several hypotheses related to the evolution of eusociality. Many single nucleotide polymorphisms that had high levels of genetic differentiation (Fst) between social and subsocial C. calcarata were in or near genes or regions important for regulating gene expression. These results are consistent with the Genetic Toolkit Hypothesis of eusocial evolution. Our findings suggest that the low behavioural complexity observed in C. calcarata may involve modulation of existing regulatory genes and gene networks to generate phenotypes associated with social behaviour.

Animals

Recently Evolved, Stage-Specific Genes Are Enriched at Life-Stage Transitions in Flies.

Understanding how genomic information is selectively utilized across different life stages is essential for deciphering the developmental and evolutionary strategies of metazoans. In holometabolous insects, the dynamic expression of genes enables distinct functional adaptations at embryonic, larval, pupal, and adult stages, likely contributing to their evolutionary success. While Drosophila melanogaster (D. melanogaster) has been extensively studied, less is known about the evolutionary dynamics that could govern stage-specific gene expression. To address this question, we compared the distribution of stage-specific genes, that is, genes expressed in temporally restricted developmental stages, across the development of D. melanogaster and Aedes aegypti (A. aegypti). Using tau-scoring, a computational method to determine gene expression specificity, we found that, on average, a large proportion of genes (20%-30% of all protein-coding genes) in both species exhibit restricted expression to specific developmental stages. Phylostratigraphy analysis, a method to date the age of genes, further revealed that stage-specific genes fall into two major categories: highly conserved and recently evolved. Notably, many of the recently evolved and stage-specific genes identified in A. aegypti and D. melanogaster are restricted to Diptera order (20%-35% of all stage-specific genes), highlighting ongoing evolutionary processes that continue to shape life-stage transitions. Overall, our findings underscore the complex interplay between gene evolutionary age, expression specificity, and morphological transformations in development. These results suggest that the attraction of genes to critical life-stage transitions is an ongoing process that may not be constant across evolutionary time or uniform between different lineages, offering new insights into the adaptability and diversification of dipteran genomes.

Animals

Comparative Transcriptomic Analyses Identify Candidate Genes for Convergent Reproductive Shifts in a Bimodal Viviparous Amphibian.

Shifts in reproductive mode represent key evolutionary innovations that shape species' life histories and evolutionary trajectories. Species showing bimodal reproductive strategies with multiple independent origins offer a rare opportunity to gain insights into the adaptive processes and mechanisms underlying convergent traits. The fire salamander, Salamandra salamandra, is the only amphibian exhibiting intraspecific variation in reproductive mode across multiple independent reproductive shifts, enabling investigation of the transition between larviparity (females give birth to aquatic larvae) and pueriparity (females give birth to fully developed terrestrial juveniles) within a single species and across different timescales. Pueriparity is an adaptive innovation that skips the aquatic larval stage, allowing individuals to exploit habitats with no available water bodies. The fire salamander is larviparous across most of its range, but pueriparity has evolved independently at least three times: once in the early Pleistocene within S. s. bernardezi in the mountains of northern Spain, and more recently on two land-bridge islands (NW Spain) inhabited by S. s. gallaica. To identify candidate genes associated with these distinct reproductive modes, we compared gene expression profiles of the uterus and oviduct of pregnant females across two independent evolutionary transitions using RNA-sequencing. We detected shared changes in maternal gene expression among pueriparous S. s. bernardezi and S. s. gallaica relative to their larviparous counterparts, in addition to differences unique to each independent evolutionary transition. Functional enrichment analyses indicated that differentially expressed genes were associated with reproductive timing, angiogenesis, and maternal signalling, consistent with the phenotypic differences observed in the uterine environment and embryonic development between the two reproductive modes. This study represents an important first step towards understanding the genomic basis of the evolution of pueriparity in a remarkable bimodal reproductive system, and provides transcriptomic resources and candidate genes for future research into the genomic architecture underlying this poorly understood adaptive trait.

Animals

Conserved function of medaka pink-eyed dilution in melanin synthesis and its divergent transcriptional regulation in gonads among vertebrates.

Medaka is emerging as a model organism for the study of vertebrate development and genetics, and its effectiveness in forward genetics should prove equal to that of zebrafish. Here, we identify by positional cloning a gene responsible for the medaka i-3 albino mutant. i-3 larvae have weakly tyrosinase-positive cells but lack strongly positive and dendritic cells, suggesting loss of fully differentiated melanophores. The region surrounding the i-3 locus is syntenic to human 19p13, but a BAC clone covering the i-3 locus contained orthologs located at 15q11-13, including OCA2 (P). Medaka P consists of 842 amino acids and shares approximately 65% identity with mammalian P proteins. The i-3 mutation is a four-base deletion in exon 13, which causes a frameshift and truncation of the protein. We detected medaka P transcripts in melanin-producing eyeballs and (putative) skin melanophores on embryos and an alternatively spliced form in the non-melanin-producing ovary or oocytes. The mouse p is similarly expressed in gonads, but not alternatively spliced. This is the first isolation of nonmammalian P, the functional mechanism of action of which has not yet been elucidated, even in mammals. Further investigation of the functions of P proteins and the regulation of their expression will provide new insight into body color determination and gene evolution.

Amino Acid Sequence

Bayesian inference of lineage trees by joint analysis of single-cell multimodal lineage-tracing data with BiLinT.

The advent of single-cell lineage-tracing technologies has enabled the simultaneous profiling of gene expression and lineage barcodes. However, accurate, high-resolution reconstruction of cell lineage trees remains challenging because most existing approaches treat these modalities separately and therefore fail to fully exploit their complementary information. Here we present BiLinT, a Bayesian framework that jointly models multimodal single-cell lineage-tracing data for lineage tree reconstruction. BiLinT integrates barcode evolution (a continuous-time Markov chain) with gene expression dynamics (an Ornstein-Uhlenbeck process) within a unified probabilistic model. Across synthetic and real data sets, BiLinT provides accurate lineage-tree reconstruction and reveals differentiation-associated clonal structure and developmental fate biases.

Journal Article

The auxin gatekeepers: Evolution and diversification of the YUCCA family.

The critically important YUCCA (YUC) gene family is highly conserved and specific to the plant kingdom, primarily responsible for the final and rate-limiting step for indole-3-acetic acid (IAA) biosynthesis. IAA is an essential phytohormone, involved in virtually all aspects of plant growth and development. In addition, IAA is involved in fine-tuning plant responses to biotic and abiotic interactions and stresses. While the YUC gene family has significantly expanded throughout the plant kingdom, a detailed analysis of the evolutionary patterns driving this diversification has not been performed. Here, we present a comprehensive phylogenetic analysis of the YUC family, combining YUCs from species representing key evolutionary plant lineages. The evolutionary history of YUCs is complex and suggests multiple recruitment events via horizontal gene transfer from bacteria. We identify and hierarchically classify the YUC family into an early diverging grade, five distinct classes and 41 subclasses. Angiosperm YUC diversity and expansion are explained in the context of protein sequence conservation, as well as spatial and gene expression patterns. The presented YUC gene landscape offers new perspectives on the distribution and evolutionary trends of this crucial family, which facilitates further YUC characterization within plant development and response to environmental change.

Indoleacetic Acids

Oncogenic roles of young human de novo genes and their potential as neoantigens in cancer immunotherapy.

Young human de novo genes, recently emerging from non-coding regions, are expected to contribute to human-specific traits and diseases. However, systematic explorations of this connection have been lacking. Here, we report 37 recently originated de novo genes in humans, with their evolution and characteristics defined within an updated genomic context. The expression of these genes is significantly upregulated and temporospatially expanded in tumors, partially associated with extrachromosomal DNA amplification. Depletion of 57.1% of these genes suppresses tumor cell proliferation, underscoring their roles in tumorigenesis. As a proof of concept, we developed mRNA vaccines expressing ELFN1-AS1 and TYMSOS-young genes specifically expressed during early development but reactivated exclusively in tumors. In humanized mice, these vaccines triggered specific T cell activation and inhibited tumor growth. The antigens derived from these genes are immunogenic and capable of eliciting antigen-specific T cell activation in colorectal cancer patients. These findings underscore young human de novo genes as neoantigens in cancer immunotherapy.

Humans

Reconstructing the 3D genome organization of Neanderthals reveals that chromatin folding shaped phenotypic and sequence divergence.

Changes in gene regulation were a major driver of the divergence of archaic hominins (AHs)-Neanderthals and Denisovans-and modern humans (MHs). The three-dimensional (3D) folding of the genome is critical for regulating gene expression; however, its role in recent human evolution has not been explored because the degradation of ancient samples does not permit experimental determination of AH 3D genome folding. To fill this gap, we apply novel deep learning methods for inferring 3D genome organization from DNA sequence to Neanderthal, Denisovan, and diverse MH genomes. Using the resulting 3D contact maps across the genome, we identify 167 distinct regions with diverged 3D genome organization between AHs and MHs. We show that these 3D-diverged loci are enriched for genes related to the function and morphology of the eye, supra-orbital ridges, hair, lungs, immune response, and cognition. Despite these specific diverged loci, the 3D genome of AHs and MHs is more similar than expected based on sequence divergence, suggesting that the pressure to maintain 3D genome organization constrained hominin sequence evolution. We also find that 3D genome organization constrained the landscape of AH ancestry in MHs today: regions more tolerant of 3D variation are enriched for introgression in modern Eurasians. Finally, we identify loci where modern Eurasians have inherited novel 3D genome folding patterns from AH ancestors and validate folding differences in a high-frequency locus using Hi-C, revealing a putative molecular mechanism for phenotypes associated with archaic introgression. In summary, our application of deep learning to predict archaic 3D genome organization illustrates the potential of inferring molecular phenotypes from ancient DNA to reveal previously unobservable biological differences.

Journal Article

The mouse neurological mutant flailer expresses a novel hybrid gene derived by exon shuffling between Gnb5 and Myo5a.

Exon shuffling is thought to be an important mechanism for evolution of new genes. Here we show that the mouse neurological mutation flailer (flr) expresses a novel gene that combines the promoter and first two exons of guanine nucleotide binding protein beta 5 (Gnb5) with the C-terminal exons of the closely linked Myosin 5A (MyoVA) gene (Myo5a). The flailer protein, which is expressed predominantly in brain, contains the N-terminal 83 amino acids of Gnb5 fused in-frame with the C-terminal 711 amino acids of MyoVA, including the globular tail domain that binds organelles for intracellular transport. Biochemical and genetic studies indicate that the flailer protein competes with wild-type MyoVA in vivo, preventing the localization of smooth endoplasmic reticulum vesicles in the dendritic spines of cerebellar Purkinje cells. The flailer protein thus has a dominant-negative mechanism of action with a recessive mode of inheritance due to the dependence of competitive binding on the ratio between mutant and wild-type proteins. The chromosomal arrangement of Myo5a upstream of Gnb5 is consistent with non-homologous recombination as the mutational mechanism. To our knowledge, flailer is the first example of a mammalian mutation caused by germ line exon shuffling between unrelated genes.

Amino Acid Sequence

Evolution of DNA methylation in the human brain.

DNA methylation is a critical regulatory mechanism implicated in development, learning, memory, and disease in the human brain. Here we have elucidated DNA methylation changes during recent human brain evolution. We demonstrate dynamic evolutionary trajectories of DNA methylation in cell-type and cytosine-context specific manner. Specifically, DNA methylation in non-CG context, namely CH methylation, has increased (hypermethylation) in neuronal gene bodies during human brain evolution, contributing to human-specific down-regulation of genes and co-expression modules. The effects of CH hypermethylation is particularly pronounced in early development and neuronal subtypes. In contrast, DNA methylation in CG context shows pronounced reduction (hypomethylation) in human brains, notably in cis-regulatory regions, leading to upregulation of downstream genes. We show that the majority of differential CG methylation between neurons and oligodendrocytes originated before the divergence of hominoids and catarrhine monkeys, and harbors strong signal for genetic risk for schizophrenia. Remarkably, a substantial portion of differential CG methylation between neurons and oligodendrocytes emerged in the human lineage since the divergence from the chimpanzee lineage and carries significant genetic risk for schizophrenia. Therefore, recent epigenetic evolution of human cortex has shaped the cellular regulatory landscape and contributed to the increased vulnerability to neuropsychiatric diseases.

Animals

Haplotype-resolved genome of Forsythia suspensa reveals the reticulate evolution in Oleaceae and a novel gene cluster regulating stamen development.

The olive family (Oleaceae) comprises numerous species of economic, horticultural, and medicinal importance. Despite its significance, the evolutionary history of this complex family remains enigmatic. Here, we generated a high-quality haplotype-resolved genome of Forsythia suspensa, a distylous species that occupies a key phylogenetic position in Oleaceae. The 2 haplotypes exhibit significant allelic divergence with potential allele-specific regulation. We reconstructed the polyploidization history of Oleaceae by confirming and precisely dating a shared whole-genome triplication and an independent whole-genome duplication event. We revealed a complex reticulate evolution that gave rise to the tribe Oleeae: an initial hybridization between Forsythieae (♂) and Jasmineae (♀), a subsequent backcrossing event, and a final whole-genome duplication. We identified a novel tandemly duplicated pectin methylesterase inhibitor gene cluster that regulates filament length and pollen size via restricting cell elongation in the long-styled morph. Dosage augmentation via stepwise cluster formation (0.99 to 3.83 Mya) may contribute to maintaining stamen traits of the long-styled morph. These FsPMEIs are co-expressed with many cell wall-related genes, suggesting a functional link in cell wall modification. Our study reveals the reticulate evolution in Oleaceae and a novel gene cluster controlling stamen development in F. suspensa and provides valuable haplotype-resolved genomic resources for heterostylous species, offering novel framework and molecular pathways to understand plant adaptive evolution.

Forsythia

TRB proteins in moss reveal their evolutionarily conserved roles in plant development and telomere maintenance.

Telomere repeat binding (TRB) proteins are plant-specific proteins with a unique domain structure distinct from telomerebinding proteins in animals and yeast. While extensively studied in seed plants, their role in early-diverging plant lineages remains largely unexplored. Here, we investigate TRB proteins in a model moss, Physcomitrium patens, to assess their evolutionary conservation and functional significance. Functional analysis using single knockout mutants revealed that individual PpTRB genes are essential for normal development, with mutants exhibiting defects in the two-dimensional (protonemal) stage, and more prominently, in the formation of three-dimensional (gametophore) structures. Some double mutants displayed telomere shortening, a phenotype also observed in TRB-deficient seed plants, indicating a conserved role for TRBs in telomere maintenance. Transcriptome profiling of TRB mutants revealed altered expression of genes associated with transcriptional regulation and stimulus response in protonema. Subcellular localization studies across various plant cell types confirmed that PpTRBs, like their seed plant counterparts, localize prevalently to the plant nucleus and mutually interact. In bryophytes, TRBs form a monophyletic group that mirrors the species phylogeny, whereas in seed plants, TRBs have diversified into two distinct monophyletic groups. Our findings provide the first comprehensive characterization of TRB proteins in non-vascular plants and demonstrate their conserved roles in telomere maintenance, with additional implications for plant development and gene regulation across land plant lineages.

Bryopsida

RNA tumor virus genes and the transforming genes: genetic transmission, infectious spread, and modes of expression.

The genetic conservation and evolution of virogenes in mammalian species are described in relation to the horizontal, vertical, and congenital transmission of type C RNA oncogenic viruses within members of a given species, or among members of near and/or distantly related species. Examples of oncogenic virus infection between ancestors of the mouse, cat, pig, and primates as well as the integration of the virus into the host's genome are documented. The possible normal functions of the virogenes as a part of the cellular genome of many species are explored. Recent evidence of genetic recombination (genetic mixing) among distinct type C viruses is also reviewed, thus completing an overview of the evolutionary past, present, and complex future relationships of oncogenic RNA viruses and mammalian species.

Animals

Selective targeting of a histone-like silencer Sfx to the R6K conjugal transfer operon.

Conjugative plasmids drive bacterial evolution and antibiotic resistance spread, yet their gene expression must be silenced to protect the host. A histone-like protein H-NS represses many mobile and sedentary xenogenes but fails to silence the conjugal transfer vir operon of R6K, a prototype IncX plasmid. Instead, R6K encodes its own H-NS homolog, Sfx, to repress the vir operon. Here, we show that, unlike other plasmid silencers that target promoters, Sfx cooperates with Rho factor to arrest transcription elongation. ChIP-seq reveals that Sfx and H-NS share similar DNA motifs and a preference for negative supercoiling, but occupy reciprocal genomic niches; Sfx is enriched on the R6K vir operon despite weak chromosomal binding, whereas H-NS displays the opposite preference. We show that Sfx binding to vir DNA critically depends on DNA topology and hypothesize that its selective targeting to R6K is mediated by Sfx-vir interactions and phase separation. Our results suggest that Sfx phase separates with R6K to ensure its preferential recruitment to the plasmid DNA and forms stable bridged nucleoprotein filaments that are impermeable to competitors such as H-NS. These findings reveal how histone-like proteins can partition the genome into distinct regulatory niches, a strategy likely mirrored across all life.

Operon

Molting in Pancrustacea Is Characterized by Both Deeply Conserved and Recently Evolved Gene Modules.

Arthropods such as insects and crustaceans, which together form the monophyletic group Pancrustacea, possess a rigid chitinous exoskeleton that must be periodically shed through molting to allow growth and morphological change. Although molting is a deeply conserved developmental process across Arthropoda, our understanding of its molecular mechanisms is still largely derived from insect model species. Lineage-specific innovations and losses of molting-related genes raise fundamental questions about the extent of its conservation outside noninsect arthropods. Here, we investigate the evolutionary conservation of molting gene expression across five representative pancrustacean species using publicly available transcriptomic datasets. Changes in gene expression during molting are characterized by both deeply conserved and lineage-specific gene modules. Temporal gene expression analyses reveal that these lineage-specific signatures are not uniformly distributed across the molting process: the middle transitional phase is more lineage-specific, thereby exhibiting an inverse hourglass pattern. This is likely due to life-history-specific processes, development of the cuticle, and specialized structures of the exoskeleton. Overall, this study provides evidence for both the evolutionary conservation and divergence of this key postembryonic developmental process and highlights the modular architecture of the molting program.

Animals