European Journal of Human Genetics最新文献

Robertsonian translocations (robs) are associated with a high risk for unbalanced segregations. Preimplantation Genetic Testing (PGT) offers an early opportunity to evaluate segregation patterns and selection against chromosome imbalances. The objective of this study was to evaluate the chromosome complements in blastocysts for male and female rob carriers and provide information useful in PGT counseling for rob carriers. PGT results were reviewed for 296 couples where a balanced and nonhomologous rob was present in one member of the couple. All embryos had day 5/6 trophectoderm biopsy and SNP-based PGT. The study included 2235 blastocysts, of which 2151 (96.2%) had results. Significantly fewer blastocysts were available for female rob carriers (mean 4.60/IVF cycle) compared to males (5.49/cycle). Male carriers were more likely to have blastocysts with a normal/balanced chromosome complement; 84.8% versus 62.8% (P < 0.00001). Male carriers had fewer blastocysts with monosomy (60/152, 39.5%) compared to female carriers (218/396, 55.1%) (P = 0.001). Twenty-one (1%) blastocysts showed 3:0 segregation; these were mostly double trisomies and derived from female carriers. Differences between chromosome complements for male versus female carriers suggest that selection against unbalanced forms may occur during spermatogenesis. Six blastocyst samples showed an unexpected ("noncanonical") combination of trisomy and monosomy. One case of uniparental disomy was identified. For female carriers, there was no association between unbalanced segregation and parental age but for male carriers, there was an inverse association. PGT is a highly beneficial option for rob carriers and patients can be counseled using our estimates for the chance of at least one normal/balanced embryo.

Pathogenic SOX11 variants have been associated with intellectual developmental disorder with microcephaly, and with or without ocular malformations or hypogonadotropic hypogonadism (HH) (IDDMOH, OMIM # 615866). In this article, we report seven new patients with de novo SOX11 variants. Five of the variants are missense, one nonsense, and one whole-gene deletion, most of them are novel variants. The main clinical features included neurodevelopmental delay (7/7) and intellectual disability (5/7), autism/attention deficit hyperactivity disorder (5/7), microcephaly (4/7), short stature (4/7), hypotonia (4/7), and clinodactyly of the 5th fingers (5/7). HH was confirmed in two female patients with primary amenorrhea, nonvisualized/prepubertal size of the uterus, and nonvisualized ovaries. Two of the male patients presented with micropenis, two had cryptorchidism, and one had decreased testicular size, which are suggestive findings of HH. This article contributes to the clinical characterization of patients with SOX11 variants and supports the role of this gene in HH.

Clinical exome sequencing (ES) has facilitated genetic diagnosis in individuals with a rare genetic disorder by analysis of all protein-coding sequences in a single experiment. However, in 40-60% of patients, a conclusive diagnosis remains elusive. In 2-5% of these individuals, ES does identify a disease-associated monoallelic variant in a recessive disorder. We hypothesized that short-read genome sequencing (GS) might uncover a pathogenic variant on the second allele, thereby increasing diagnostic yield. We performed GS for 174 individuals in whom ES identified a monoallelic pathogenic variant in a gene associated with recessive disease related to their phenotype. GS interpretation was limited to the (non-)coding parts of the gene in which this first pathogenic variant was identified, focusing on splice-disrupting variants. Firstly, we uncovered a second pathogenic variant affecting coding sequence in five individuals, including two SNV/indel variants, two copy number variants, and one insertion. Secondly, for 24 individuals, we identified a total of 31 rare non-coding intronic SNV/indel variants, all predicted to disrupt splicing. Using functional follow-up assays, we confirmed an effect on splicing for three of these variants (in ABCA4, POLR3A and COL4A4) in three individuals. In summary, we identified a (likely) pathogenic second variant in 4.6% (8/174), and a possible diagnosis for 12.1% (21/174) of our cohort. Hence, when performing GS as first-tier diagnostic test, including the interpretation of SVs and rare intronic variants in known recessive disease genes, the overall diagnostic yield of rare disease will increase. The added diagnostic value of GS for recessive disease In our cohort of 174 individuals (84 males and 90 females) with a monoallelic pathogenic variant in genes associated with a wide and diverse range of recessive diseases (pie chart), using genome sequencing (GS) and a systematic approach (methods), we identified eight new diagnoses (4.6%). We identified a second likely pathogenic variant in eight individuals (results); In two a second coding variant was found, in three others, a rare non-coding SNV anticipated to disrupt splicing was uncovered, and in three individuals a structural rearrangement was identified (two copy number variants (CNV), and one structural variant (SV)).

Establishing a molecular diagnosis remains challenging in half of individuals with childhood-onset neuromuscular diseases (NMDs) despite exome sequencing. This study evaluates the diagnostic utility of combining genomic approaches in undiagnosed NMD patients. We performed deep phenotyping of 58 individuals with unsolved childhood-onset NMDs that have previously undergone inconclusive exome studies. Genomic approaches included trio genome sequencing and RNASeq. Genetic diagnoses were reached in 23 out of 58 individuals (40%). Twenty-one individuals carried causal single nucleotide variants (SNVs) or small insertions and deletions, while 2 carried pathogenic structural variants (SVs). Genomic sequencing identified pathogenic variants in coding regions or at the splice site in 17 out of 21 resolved cases, while RNA sequencing was additionally required for the diagnosis of 4 cases. Reasons for previous diagnostic failures included low coverage in exonic regions harboring the second pathogenic variant and involvement of genes that were not yet linked to human diseases at the time of the first NGS analysis. In summary, our systematic genetic analysis, integrating deep phenotyping, trio genome sequencing and RNASeq, proved effective in diagnosing unsolved childhood-onset NMDs. This approach holds promise for similar cohorts, offering potential improvements in diagnostic rates and clinical management of individuals with NMDs.

Oculo-auriculo-vertebral spectrum (OAVS) is characterized by abnormal development of the 1st and 2nd branchial arches. Despite arguments against a monogenic condition, a few genes have been involved in a minority of cases. We now report heterozygous, presumably loss-of function variants in the CHAF1A gene in 8 individuals, including 3 members of the same family. Four cases fulfill stringent diagnostic criteria for OAVS, including asymmetric ear dysplasia, preauricular tags, mandibular asymmetry +/- vertebral malformations. Two patients also presented with kidney malformations. CHAF1A encodes a subunit of CAF-1 (chromatin assembly factor-1), a heterotrimeric protein complex responsible for the deposition of newly synthesized histones H3-H4 onto the newly synthetized DNA strand during replication. The identification of loss-of-unction variants in CHAF1A is consistent with the hypothesis of early developmental genes dysregulation driving OAVS and other associations recently lumped under the acronym Recurrent Constellations of Embryonic Malformations (RCEM).

Despite extensive research into the genetic underpinnings of neurodevelopmental disorders (NDD), many clinical cases remain unresolved. We studied a female proband with a NDD, mildly dysmorphic facial features, and brain stem hypoplasia on neuroimaging. Comprehensive genomic analyses revealed a terminal 5p loss and a terminal 18q gain in the proband while a diploid copy number for chromosomes 5 and 18 in both parents. Genomic investigations in the proband identified an unbalanced translocation t(5;18) with additional genetic material from chromosome 2 (2q31.3) inserted at the breakpoint, pointing to a complex chromosomal rearrangement (CCR) involving 5p15.2, 2q31.3, and 18q21.32. Breakpoint junction analyses enabled by long-read genome sequencing unveiled the presence of four distinct junctions in the father, who is a carrier of a balanced CCR. The proband inherited from the father both the abnormal chromosome 5 resulting in segmental aneusomies of chr5 (loss) and chr18 (gain) and a der(2) homologue. Evidences suggest a chromoplexy mechanism for this CCR derivation, involving double-strand breaks (DSBs) repaired by non-homologous end joining (NHEJ) or alternative end joining (alt-EJ). The complexity of the CCR and the segregation of homologues elucidate the genetic model for this family. This study demonstrates the importance of combining multiple genomic technologies to uncover genetic causes of complex neurodevelopmental syndromes and to better understand genetic disease mechanisms.