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Hereditary hypophosphataemic rickets with autosomal recessive inheritance and severe osteosclerosis. A report of two cases.

We have observed congenital hypophosphataemic rickets in two sons of a marriage between first cousins, their mother being clinically and biochemically normal. Both patients are now approaching middle age. In addition to severe childhood rickets and lifelong hypophosphataemia, their disease is characterised by gross osteosclerosis with extraskeletal ossification, clinically persistent osteomalacia in one and spinal cord compression in the other. The genetics of this disease can be satisfactorily explained only on the basis of autosomal recessive inheritance, a mode which has only once before been reported in the literature. The severity of certain features, which would be expected in a homozygous state, may help our understanding of the more usual X-linked form.

Adult↗

Pathogenesis and phenotypes of an X-linked recessive lymphoproliferative syndrome.

A new X-linked recessive lymphoproliferative syndrome has variable phenotypes: fatal infectious mononucleosis (I.M.), agammaglobulinaemia after I.M., American Burkitt's lymphoma, histiocytic lymphoma, immunoblastic sarcoma of B cells, or plasmacytoma. An immunodeficiency to rubeola and the Epstein-Barr virus probably ensues from the mutant gene. The phenotypes (spectrum of B-cell disorders) have a common inheritance and the aetiology is similar.

Adolescent↗

Perspective on Adeno-Associated Virus Capsid Modification for Duchenne Muscular Dystrophy Gene Therapy.

Duchenne muscular dystrophy (DMD) is a X-linked, progressive childhood myopathy caused by mutations in the dystrophin gene, one of the largest genes in the genome. It is characterized by skeletal and cardiac muscle degeneration and dysfunction leading to cardiac and/or respiratory failure. Adeno-associated virus (AAV) is a highly promising gene therapy vector. AAV gene therapy has resulted in unprecedented clinical success for treating several inherited diseases. However, AAV gene therapy for DMD remains a significant challenge. Hurdles for AAV-mediated DMD gene therapy include the difficulty to package the full-length dystrophin coding sequence in an AAV vector, the necessity for whole-body gene delivery, the immune response to dystrophin and AAV capsid, and the species-specific barriers to translate from animal models to human patients. Capsid engineering aims at improving viral vector properties by rational design and/or forced evolution. In this review, we discuss how to use the state-of-the-art AAV capsid engineering technologies to overcome hurdles in AAV-based DMD gene therapy.

Animals↗

The electroretinogram in retinitis pigmentosa.

Examination of electroretinographic (ERG) reports from 70 consecutive patients with retinitis pigmentosa (RP) showed that photopic and scotopic B-wave amplitudes correlated with age and visual acuity, but not with dark adaptation threshold. No appreciable differences in ERG characteristics (including B-wave implicit time) were observed between recessive, dominant, and X-linked cases. However, the ERG findings from one group of patients stood out clearly from the rest, because of normal flicker B-wave implicit times (less than or equal to 32 ms) and large B-wave amplitudes (less than or equal to 100 muV under scotopic conditions). These patients constitute a recognizable subgroup of RP, independent of the mode of inheritance, which is characterized by delimited disease, mild functional symptoms, and a good visual prognosis.

Adolescent↗

Genetic control of immune responsiveness in man.

Interest in immunogenetics originated from two streams: (a) histocompatibility in mouse and man, and (b) inheritance of specific immune responses in the guinea pig and mouse. In the mouse, there are genes associated with the major histocompatibility complex (MHC) which (i) code for antigens determining allograft responses and mixed lymphocyte reactions, (ii) control responses to certain antigens (Ir genes), and (iii) code for cell-surface antigens which elicit specific antisera (anti-Ia). In man, there is genetic control, in part X-linked, over levels of immunoglobulins and immunoglobulin classes. Evidence for MHC-linked genetic control is derived from immune responses to (i) micro-organisms, (ii) pollen antigens, (iii) food antigens, (iv) vaccines, (v) inocuous test antigens, and (vi) autoantigens. Some evidence exists for allotype-linked genetic control. Practical aspects concern influences of the MHC on susceptibility to disease, within individuals and populations.

Antibody Formation↗

Early-Onset Atrial Fibrillation and the Prevalence of Rare Variants in Cardiomyopathy and Arrhythmia Genes.

IMPORTANCE: Early-onset atrial fibrillation (AF) can be the initial manifestation of a more serious underlying inherited cardiomyopathy or arrhythmia syndrome. OBJECTIVE: To examine the results of genetic testing for early-onset AF. DESIGN, SETTING, AND PARTICIPANTS: This prospective, observational cohort study enrolled participants from an academic medical center who had AF diagnosed before 66 years of age and underwent whole genome sequencing through the National Heart, Lung, and Blood Institute's Trans-Omics for Precision Medicine program. Participants were enrolled from November 23, 1999, to June 2, 2015. Data analysis was performed from October 24, 2020, to March 11, 2021. EXPOSURES: Rare variants identified in a panel of 145 genes that are included on cardiomyopathy and arrhythmia panels used by commercial clinical genetic testing laboratories. MAIN OUTCOMES AND MEASURES: Sequencing data were analyzed using an automated process followed by manual review by a panel of independent, blinded reviewers. The primary outcome was classification of rare variants using American College of Medical Genetics and Genomics criteria: benign, likely benign, variant of undetermined significance, likely pathogenic, or pathogenic. Disease-associated variants were defined as pathogenic/likely pathogenic variants in genes associated with autosomal dominant or X-linked dominant disorders. RESULTS: Among 1293 participants (934 [72.2%] male; median [interquartile range] age at enrollment, 56 [48-61] years; median [interquartile range] age at AF diagnosis, 50 [41-56] years), genetic testing identified 131 participants (10.1%) with a disease-associated variant, 812 (62.8%) with a variant of undetermined significance, 92 (7.1%) as heterozygous carriers for an autosomal recessive disorder, and 258 (20.0%) with no suspicious variant. The likelihood of a disease-associated variant was highest in participants with AF diagnosed before the age of 30 years (20 of 119 [16.8%; 95% CI, 10.0%-23.6%]) and lowest after the age of 60 years (8 of 112 [7.1%; 95% CI, 2.4%-11.9%]). Disease-associated variants were more often associated with inherited cardiomyopathy syndromes compared with inherited arrhythmias. The most common genes were TTN (n = 38), MYH7 (n = 18), MYH6 (n = 10), LMNA (n = 9), and KCNQ1 (n = 8). CONCLUSIONS AND RELEVANCE: In this cohort study, genetic testing identified a disease-associated variant in 10% of patients with early-onset AF (the percentage was higher if diagnosed before the age of 30 years and lower if diagnosed after the age of 60 years). Most pathogenic/likely pathogenic variants are in genes associated with cardiomyopathy. These results support the use of genetic testing in early-onset AF.

Adult↗

Identification of a novel non-coding deletion in Allan-Herndon-Dudley syndrome by long-read HiFi genome sequencing.

BACKGROUND: Allan-Herndon-Dudley syndrome (AHDS) is an X-linked disorder caused by pathogenic variants in the SLC16A2 gene. Although most reported variants are found in protein-coding regions or adjacent junctions, structural variations (SVs) within non-coding regions have not been previously reported. METHODS: We investigated two male siblings with severe neurodevelopmental disorders and spasticity, who had remained undiagnosed for over a decade and were negative from exome sequencing, utilizing long-read HiFi genome sequencing. We conducted a comprehensive analysis including short-tandem repeats (STRs) and SVs to identify the genetic cause in this familial case. RESULTS: While coding variant and STR analyses yielded negative results, SV analysis revealed a novel hemizygous deletion in intron 1 of the SLC16A2 gene (chrX:74,460,691 - 74,463,566; 2,876 bp), inherited from their carrier mother and shared by the siblings. Determination of the breakpoints indicates that the deletion probably resulted from Alu/Alu-mediated rearrangements between homologous AluY pairs. The deleted region is predicted to include multiple transcription factor binding sites, such as Stat2, Zic1, Zic2, and FOXD3, which are crucial for the neurodevelopmental process, as well as a regulatory element including an eQTL (rs1263181) that is implicated in the tissue-specific regulation of SLC16A2 expression, notably in skeletal muscle and thyroid tissues. CONCLUSIONS: This report, to our knowledge, is the first to describe a non-coding deletion associated with AHDS, demonstrating the potential utility of long-read sequencing for undiagnosed patients. Although interpreting variants in non-coding regions remains challenging, our study highlights this region as a high priority for future investigation and functional studies.

Humans↗

Mus musculus x Mus caroli hybrids: mouse mules.

Analysis of six enzymes using starch gel electrophoresis indicates that autosomal and X-linked genes of both parental species are expressed normally in M. musculus X M. caroli hybrids. There is no evidence for allelic repression for the four autosomally inherited enzymes. Banding patterns for G6PD and PGK-1 indicate that X-chromosome inactivation occurs and that the maternally derived M. musculus X-chromosome is preferentially expressed in the yolk sac. Despite normal genetic expression none of the four adult female hybrids was fertile and the male hybrids tended to be retarded during fetal development. The routine production of fetal M. musculus X M. caroli hybrids, heterozygous for three X-linked genes coding for G6PD, PGK-1, and HPRT, should provide an excellent system for the analysis of X-chromosome expression and an alternative to the mule for studies of hybrid reproduction and development.

Animals↗

35 Individuals With HUWE1-Related Neurodevelopmental Disorder and Suggested Clinical Evaluations.

HUWE1 (HECT, UBA, and WWE Domain Containing E3 Ubiquitin Protein Ligase1, OMIM 300697), located at Xp11.22, encodes a ubiquitin ligase that is highly conserved across species. Genetic variants in HUWE1 described in multiple independent studies cause X-linked intellectual disability, including in the patients identified by Juberg, Marsidi, and Brooks. This report describes 35 additional cases of individuals with variants in HUWE1 and suggested guidelines for clinical management. Our study includes several female cases, which have not been widely reported previously. Our findings confirm earlier reported clinical features including developmental delay, autism, hypotonia, short stature, and dysmorphic facial features as well as additional multisystemic findings. Intrauterine growth restriction (IUGR) and feeding difficulties were common in the neonatal period. It is notable that nearly all females had de novo variants, and males had de novo or inherited variants from clinically unaffected carrier mothers. Three genetic hotspots were identified in evolutionarily conserved regions of HUWE1 that have clinical impact. This report provides additional characterization of the spectrum of HUWE1-related neurodevelopmental disorder (HNDD).

Humans↗

Inherited congenital normofunctional testicular hyperplasia and mental deficiency. A corroborative study.

Three 46,XY unrelated individuals out of 84 postpubertal male inpatients with severe mental deficiency in a psychiatric hospital were found to have megalorchidia and macrogenitosomia. One of the cases had a similarly affected brother. Endocrine studies were performed in two of the cases with similar results. Normal plasma levels of pituitary gonadotropins were found. A normal testicular function was demonstrated by the finding of normal: (a) baseline plasma testosterone levels and a significant rise following human chorionic gonadotropin administration, (b) sperm analysis, and (c) morphology and cell architecture of the testes. These results were compatible with normofunctional testicular hyperplasia confirming previous observations and allowing the definite individualization of a syndrome with mental deficiency probably due to an X-linked recessive mutation.

Adult↗

Identifying inversions with breakpoints in the Dystrophin gene through long-read sequencing: report of two cases.

BACKGROUND: Duchenne Muscular Dystrophy (DMD) is an X-linked disorder caused by mutations in the DMD gene, with large deletions being the most common type of mutation. Inversions involving the DMD gene are a less frequent cause of the disorder, largely because they often evade detection by standard diagnostic methods such as multiplex ligation probe amplification (MLPA) and whole exome sequencing (WES). CASE PRESENTATION: Our research identified two intrachromosomal inversions involving the dystrophin gene in two unrelated families through Long-read sequencing (LRS). These variants were subsequently confirmed via Sanger sequencing. The first case involved a pericentric inversion extending from DMD intron 47 to Xq27.3. The second case featured a paracentric inversion between DMD intron 42 and Xp21.1, inherited from the mother. In both cases, simple repeat sequences (SRS) were present at the breakpoints of these inversions. CONCLUSIONS: Our findings demonstrate that LRS is an effective tool for detecting atypical mutations. The identification of SRS at the breakpoints in DMD patients enhances our understanding of the mechanisms underlying structural variations, thereby facilitating the exploration of potential treatments.

Humans↗

EGFLAM Pathogenic Variants and Congenital Stationary Night Blindness.

IMPORTANCE: Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous inherited retinal disorder (IRD), and in many complete CSNB (cCSNB) cases, the underlying genetic cause remains unknown. Uncovering the genetic defects of IRDs helps to refine diagnostic methods and supports the development of specific therapeutic approaches. OBJECTIVE: To describe the phenotype and the underlying gene defect in patients with cCSNB from 2 unrelated families. DESIGN, SETTING AND PARTICIPANTS: This retrospective case series was conducted from January 2023 to July 2025. Data for 3 patients from cohorts of genetically unsolved IRD cases in France (n = 140 for CSNB) and the Netherlands (n = 2730 for IRD) were analyzed clinically and genetically. EXPOSURES: Complete ocular examination, including multimodal retinal imaging and full-field electroretinography (ffERG) incorporating the International Society for Clinical Electrophysiology of Vision standards and multimodal retinal imaging, were performed. Gene defects were identified by genome sequencing (GS) and exome sequencing (ES). MAIN OUTCOMES AND MEASURES: The main outcome was a gene defect, EGFLAM, underlying cCSNB. Measures included phenotyping, GS, ES, Sanger sequencing, and cosegregation analysis. RESULTS: The series included 3 patients from 2 unrelated families of Moroccan ancestry showing high myopia, reduced visual acuity, and night blindness. Retinal imaging depicted myopic changes. ffERG revealed electronegative Schubert-Bornschein configuration in keeping with cCSNB with ON-bipolar cell dysfunction. Patients were lacking pathogenic variants in known genes implicated in IRDs, including CSNB. Two different homozygous pathogenic variants, c.1563_1566del, p.(Val522Glufs*18) and c.1795C>T, p.(Arg599*) in EGFLAM were identified by ES and GS. The corresponding protein is localized in the outer plexiform layer and important for ON-bipolar cell signaling in the retina. CONCLUSION AND RELEVANCE: This case series reports on a gene defect in EGFLAM implicated in human cCSNB. Clinicians should be aware about this association and consider including EGFLAM in diagnostic gene panels for IRDs. This discovery may lead to faster and more accurate diagnosis of cCSNB and genetic counseling, as well as a pathway for developing therapies.

Adolescent↗

Testis-determining H-Y antigen in XO males of the mole-vole (Ellobius lutescens).

The XO sex chromosome constitution has been found in both sexes of the mole-vole (Ellobius lutescens) belonging to the rodent family Microtinae. This enigmatic species has apparently been enduring a 50% zygotic lethality. The current serological study revealed the presence in XO males and the absence from XO females of H-Y (histocompatibility Y) antigen. In all the mammalian species studied thus far, the expression of H-Y antigen strictly coincided with the presence of testicular tissue and not necessarily with the presence of the Y chromosome. The testis-organizing function of the H-Y gene appears to have been confirmed. In the mole-vole, X linkage of the testis-organizing H-Y gene is favored over its autosomal inheritance. Only X linkage of the H-Y gene creates a compelling evolutionary need to change the female sex chromosome constitution from XX to XO, and to abandon the dosage compensation by an X inactivation mechanism, so that the nonproductive XH-YX zygote can be eliminated as an embryonic lethal. With regard to the electrophoretic mobilities of three X-linked marker enzymes, however, a genetic difference between the male-specific XH-Y and the female-specific X was not detected. This might reflect a relatively recent speciation.

Animals↗

X-linked recessive progressive combined variable immunodeficiency (Duncan's disease).

Of 18 boys in Duncan kindred, 6 died of a lymphoproliferative disease. They exhibited a subtle, progressive combined variable immunodeficiency disease characterised by benign or malignant proliferation of lymphocytes, histiocytosis, and alterations in concentrations of serum-immunoglobulins. Infectious mononucleosis occurred during or preceding terminal events in at least 3 of the cousins. Fever, pharyngitis, lymphadenomegaly, hepatosplenomegaly, atypical lymphocytosis, and a spectrum ranging from agammaglobulinaemia to polyclonal hyper-gammaglobulinaemia occurred. At necropsy, the thymus gland and thymic-dependent areas in the lymph-nodes and spleen were depleted of lymphocytes. Diffuse infiltrates composed of lymphocytes, plasma cells, and histiocytes, some containing erythrocytes, invaded the haematopoietic organs, viscera, and central nervous system. In addition, 2 half-brothers had lymphomas of the ileum and central nervous system. Approximately half the boys, including the half-brothers, were affected, and girls were spared, implying sex-linked recessive inheritance. Various lymphohistiocytoses resemble Duncan's disease, but it is distinctive from them in the mode of inheritance or by histiological characteristics. This study suggests that the Epstein-Barr virus or other viruses triggered the fatal proliferation of lymphocytes and that progressive attrition of T-cell functions allowed uncontrolled lymphoproliferation.

Adult↗

LINE-1 repeats are a defining feature of the Xce.

During early development, female mammals inactivate one X chromosome to balance their X-linked gene dosage with males. While allelic choice is random in inbred mouse populations, choice can be significantly skewed in interstrain hybrids. The genetic basis of skewing has long been attributed to the mysterious "X chromosome controlling element(s)" (Xce) with different strengths among species, subspecies, and strains. When two X-chromosomes with different Xce strengths are inherited by offspring, the X chromosome with the stronger Xce will have a higher probability of remaining active. Here, we provide evidence that L1Tf repeats-a subfamily of long interspersed nuclear elements 1-plays a role in determining Xce strength. L1Tf elements form a condensed core within the inactive X (Xi) territory. Mouse strains with varying Xce strengths differ in the L1Tf copy number on the X chromosome, with the strength of the Xce allele being inversely related to L1Tf copy number. L1Tf expression mediates the Xce effect. However, in contrast to a prior report, L1Tf RNA does not coat the Xi. Rather, L1Tf promotes condensation of the Xi core. Intriguingly, L1Tfs recruit and sequester YY1 from active genes, accelerating XCI in cis. Thus, L1Tf copy number, expression, and binding of YY1 are key defining features of the Xce. We propose a model in which the Xce influences the choice of Xist alleles by promoting YY1 binding to the nucleation site for the initiation of Xist spreading.

Animals↗

X-linked and autosomal genes controlling mouse alpha-galactosidase expression.

Analysis of F2 and backcross animals has confirmed the X-chromosome linkage of Ags, the structural locus for mouse alpha-galactosidase. The position of Ags has been located in the X chromosome, 9 centimorgans from Mo, and the gene order is centromere-Hq-Bn-Ta-Mo-Ags. A variation in the developmental expression of alpha-galactosidase activity, inherited as an autosomal trait, has been characterized using recombinant inbred lines of mice. Among certain recombinant inbred lines, the variation appears to segregate as a single major locus.

Animals↗

X-Y translocation in a retarded phenotypic male. Clinical, cytogenetic, biochemical, and serogenetic studies.

Cytogenetic studies on a mentally retarded boy revealed an X-Y translocation, karyotype 46,X,t(X;Y)(p22;q11). Only 5 other such cases have been reported and these were all females. The unequivocal male phenotype suggested non-random inactivation of the normal maternally derived X chromosome, and that the non-inactivated X-Y translocation chromosome included the locus for male determination. Confirmation of this was provided by unassociated X and Y chromatin in interphase cells, as well as by reverse banding after BrdU incorporation and autoradiography of metaphase chromosomes. There was anomalous Xg blood group inheritance in the proband, indicating possible localisation of the Xg locus to the terminal portion of the X short arm. Linkage of Xg and a form of X-linked mental retardation is suggested. Close linkage of the Xg locus with the loci for alpha-galactosidase, phosphoglycerate kinase, G-6-PD, and MPS II was excluded.

Blood Group Antigens↗

Evidence for X-linkage of phosphoribosylpyrophosphate synthetase in man. Studies with cultured fibroblasts from a gouty family with mutant feedback-resistant enzyme.

Skin fibroblast cultures were utilized to study the mode of inheritance of a mutant feedback-resistant phosphoribosylpyrophosphate synthetase in a gouty family with purine overproduction. Selective conditions were applied to allow the survival in culture of mutant cells only. Whereas in the male gouty propositus the cell culture was homogenous for the mutant enzyme, in the cell culture from his nongouty mother two cell populations were demonstrated, one normal and the other mutant. The mosaicism in the mother is compatible with X-linkage of the enzyme. From this finding, together with the clinical and biochemical data available, it is concluded that in this family the enzyme mutation is transmitted in a X-linked recessive pattern.

Adolescent↗