Role of chromosomal imbalances in the pathogenesis of DSD: A retrospective analysis of 115 prenatal samples

Differences of sex development (DSDs) are a group of congenital conditions characterized by a discrepancy between chromosomal, gonadal, and genital sex development of an individual, with significant impact on medical, psychological and reproductive life. The genetic heterogeneity of DSDs complicates the diagnosis and almost half of the patients remains undiagnosed. In this context, chromosomal imbalances in syndromic DSD patients may help to identify new genes implicated in DSDs. In this study, we aimed at describing the burden of chromosomal imbalances including submicroscopic ones (copy number variants or CNVs) in a cohort of prenatal syndromic DSD patients, and review their role in DSDs. Our patients carried at least one pathogenic or likely pathogenic chromosomal imbalance/CNV or low-level mosaicism for aneuploidy. Almost half of the cases resulted from an unbalanced chromosomal rearrangement. Chromosome 9p/q, 4p/q, 3q and 11q anomalies were more frequently observed. Review of the literature confirmed the causative role of CNVs in DSDs, either in disruption of known DSD-causing genes (SOX9, NR0B1, NR5A1, AR, ATRX, …) or as a tool to suspect new genes in DSDs (HOXD cluster, ADCY2, EMX2, CAMK1D, …). Recurrent CNVs of regulatory elements without coding sequence content (i.e. duplications/deletions upstream of SOX3 or SOX9) confirm detection of CNVs as a mean to explore our non-coding genome. Thus, CNV detection remains a powerful tool to explore undiagnosed DSDs, either through routine techniques or through emerging technologies such as long-read whole genome sequencing or optical genome mapping.

The TALE never ends: A comprehensive overview of the role of PBX1, a TALE transcription factor, in human developmental defects

PBX1 is a highly conserved atypical homeodomain transcription factor (TF) belonging to the TALE (three amino acid loop extension) family. Dimerized with other TALE proteins, it can interact with numerous partners and reach dozens of regulating sequences, suggesting its role as a pioneer factor. PBX1 is expressed throughout the embryonic stages (as early as the blastula stage) in vertebrates. In human, PBX1 germline variations are linked to syndromic renal anomalies (CAKUTHED). In this review, we summarized available data on PBX1 functions, PBX1-deficient animal models, and PBX1 germline variations in humans. Two types of genetic alterations were identified in PBX1 gene. PBX1 missense variations generate a severe phenotype including lung hypoplasia, cardiac malformations, and sexual development defects (DSDs). Conversely, truncating variants generate milder phenotypes (mainly cryptorchidism and deafness). We suggest that defects in PBX1 interactions with various partners, including proteins from the HOX (HOXA7, HOXA10, etc.), WNT (WNT9B, WNT3), and Polycomb (BMI1, EED) families are responsible for abnormal proliferation and differentiation of the embryonic mesenchyme. These alterations could explain most of the defects observed in humans. However, some phenotype variability (especially DSDs) remains poorly understood. Further studies are needed to explore the TALE family in greater depth.

Pseudodicentric Chromosome Originating from an X-Autosome Translocation in a Male Patient with Cryptozoospermia

Genetic factors are responsible for 15% of male infertility conditions. Numerical and structural chromosomal anomalies are validated genetic factors leading to spermatogenic quantitative defects, with a frequency depending on the severity of the phenotype. Among the structural chromosomal rearrangements, dicentric chromosomes are generally observed in robertsonian translocations or in cases of Y chromosome isodicentrics. In X-autosome translocations, male carriers are generally infertile, regardless of the position of the breakpoint, due to interrupted spermatogenesis. We report an infertile man bearing an unusual balanced (X;22) translocation, with a centromeric X breakpoint generating a derivative pseudodicentric chromosome psu dic(22;X). Extensive cytogenetic analyses were necessary to determine the precise nature of the derivative chromosome. The likely cause of the reproductive phenotype of the patient is discussed based on meiotic chromosomal conformation.

Prenatal phenotype of 22q11 micro-duplications: A systematic review and report on 12 new cases

The 22q11 region is prone to generating recurring Copy Number Variations (CNVs) as a result of the large numbers of Low Copy Repeats (LCRs). Typical duplications encompass the LCR-A-to-D region but atypical duplications of various sizes have also been reported. These duplications are responsible for highly variable phenotypes with incomplete penetrance and expressivity, which is challenging for adequate genetic counselling, especially in the prenatal period. To better delineate prenatal phenotypes associated with these CNVs, we report here a clinical and molecular description of twelve cases (9 foetuses and 3 deceased new-borns babies) carrying recurrent 22q11 duplications (diagnosed via aCGH), along with a review of the existing literature. 22q11 duplications were inherited from an apparently healthy parent in almost 60% of the cases. Other CNVs were diagnosed for 8% of the cases. Increased nuchal translucency and cardiac anomalies (CHD) were the most prominent phenotypes observed, along with mild renal and skeletal anomalies. Duplications encompassing the LCR-C-to-D region (and the CRKL gene) seemed more likely to generate CHDs and renal malformations. Cleft lip/palate were observed in foetuses with duplications encompassing the LCR-A-to-B region or the SPECC1L gene, as previously suggested. However, genotype-phenotype correlations remain difficult to ascertain. Second-hit point variants, epigenetic or environmental variations could play a role in the phenotypic variability of 22q11 duplications, but remain a challenge for assessment in the short period of pregnancy.

Terminal 6q deletions cause brain malformations, a phenotype mimicking heterozygous DLL1 pathogenic variants: A multicenter retrospective case series

OBJECTIVE

Terminal 6q deletion is a rare genetic condition associated with a neurodevelopmental disorder characterized by intellectual disability and structural brain anomalies. Interestingly, a similar phenotype is observed in patients harboring pathogenic variants in the DLL1 gene. Our study aimed to further characterize the prenatal phenotype of this syndrome as well as to attempt to establish phenotype-genotype correlations.

METHOD

We collected ultrasound findings from 22 fetuses diagnosed with a pure 6qter deletion. We reviewed the literature and compared our 22 cases with 14 fetuses previously reported as well as with patients with heterozygous DLL1 pathogenic variants.

RESULTS

Brain structural alterations were observed in all fetuses. The most common findings (>70%) were cerebellar hypoplasia, ventriculomegaly, and corpus callosum abnormalities. Gyration abnormalities were observed in 46% of cases. Occasional findings included cerebral heterotopia, aqueductal stenosis, vertebral malformations, dysmorphic features, and kidney abnormalities.

CONCLUSION

This is the first series of fetuses diagnosed with pure terminal 6q deletion. Based on our findings, we emphasize the prenatal sonographic anomalies, which may suggest the syndrome. Furthermore, this study highlights the importance of chromosomal microarray analysis to search for submicroscopic deletions of the 6q27 region involving the DLL1 gene in fetuses with these malformations.

Multicolor-FISH Characterization of a Prenatal Mosaicism for a Chromosomal Rearrangement Undetected by Molecular Cytogenetics

Fetal mosaicism for chromosomal rearrangements remains a challenge to diagnose, even in the era of whole-genome sequencing. We present here a case of fetal mosaicism for a chromosomal rearrangement explored in amniocytes and fetal muscle, consisting of a major cell population (95%) with partial monosomy 4q and a minor population (5%) with additional material replacing the 4qter deleted segment. Molecular techniques (MLPA, array-CGH) failed to assess the origin of this material. Only multicolor-FISH identified the additional segment on chromosome 4 as derived from chromosome 17. Due to the poor prognosis, the couple chose to terminate the pregnancy. Because of low-level mosaicism, chromosomal microarray analysis (CMA), now considered as first-tier prenatal genetic analysis, did not allow the identification of the minor cell line. In case of large CNVs (>5 Mb) detected by CMA, karyotyping may be considered to elucidate the mechanism of the underlying rearrangement and eliminate mosaicism.

Pathogenic variants in KCNQ2 cause intellectual deficiency without epilepsy: Broadening the phenotypic spectrum of a potassium channelopathy

High-throughput sequencing (HTS) improved the molecular diagnosis in individuals with intellectual deficiency (ID) and helped to broaden the phenotype of previously known disease-causing genes. We report herein four unrelated patients with isolated ID, carriers of a likely pathogenic variant in KCNQ2, a gene usually implicated in benign familial neonatal seizures (BFNS) or early onset epileptic encephalopathy (EOEE). Patients were diagnosed by targeted HTS or exome sequencing. Pathogenicity of the variants was assessed by multiple in silico tools. Patients' ID ranged from mild to severe with predominance of speech disturbance and autistic features. Three of the four variants disrupted the same amino acid. Compiling all the pathogenic variants previously reported, we observed a strong overlap between variants causing EOEE, isolated ID, and BFNS and an important intra-familial phenotypic variability, although missense variants in the voltage-sensing domain and the pore are significantly associated to EOEE (p < 0.01, Fisher test). Thus, pathogenic variants in KCNQ2 can be associated with isolated ID. We did not highlight strong related genotype-phenotype correlations in KCNQ2-related disorders. A second genetic hit, a burden of rare variants, or other extrinsic factors may explain such a phenotypic variability. However, it is of interest to study encephalopathy genes in non-epileptic ID patients.

Bardet-Biedl syndrome: Antenatal presentation of forty-five fetuses with biallelic pathogenic variants in known Bardet-Biedl syndrome genes

Bardet-Biedl syndrome (BBS) is an emblematic ciliopathy associated with retinal dystrophy, obesity, postaxial polydactyly, learning disabilities, hypogonadism and renal dysfunction. Before birth, enlarged/cystic kidneys as well as polydactyly are the hallmark signs of BBS to consider in absence of familial history. However, these findings are not specific to BBS, raising the problem of differential diagnoses and prognosis. Molecular diagnosis during pregnancies remains a timely challenge for this heterogeneous disease (22 known genes). We report here the largest cohort of BBS fetuses to better characterize the antenatal presentation. Prenatal ultrasound (US) and/or autopsy data from 74 fetuses with putative BBS diagnosis were collected out of which molecular diagnosis was established in 51 cases, mainly in BBS genes (45 cases) following the classical gene distribution, but also in other ciliopathy genes (6 cases). Based on this, an updated diagnostic decision tree is proposed. No genotype/phenotype correlation could be established but postaxial polydactyly (82%) and renal cysts (78%) were the most prevalent symptoms. However, autopsy revealed polydactyly that was missed by prenatal US in 55% of the cases. Polydactyly must be carefully looked for in pregnancies with apparently isolated renal anomalies in fetuses.

Pseudodicentric Chromosome Originating from Autosomes 9 and 21 in a Male Patient with Oligozoospermia

Genetic factors are responsible for 15% of male infertility conditions. Numerical and structural chromosomal anomalies (related to the Y chromosome or to the autosomes) are validated genetic factors leading to spermatogenic quantitative defects with a frequency depending on the severity of the phenotype. The most frequent structural chromosomal rearrangements of autosomes are translocations and inversions, whereas dicentric chromosomes involving autosomes are rare. We report a man bearing a pseudodicentric chromosome (9;21) and presenting with oligozoospermia. Extensive cytogenetic analyses were necessary to determine the precise nature of the derivative chromosome and to discount the presence of interstitial telomeric sequences. Defects in spermatogenesis and abnormal segregation at meiosis for existing spermatozoa are proposed and are the likely cause of the reproductive phenotype of the patient.

Le sexisme en archéologie, ça n’existe pas

Les archéologues sont confronté·e·s à de nombreuses questions éthiques dans leur pratique quotidienne ; ces questionnements portent aussi sur leurs pratiques et sur leurs comportements vis-à-vis de leurs pairs. La mise en lumière des discriminations liées au genre, parfois combinées à d’autres éléments tels que l’ethnicité, l’orientation sexuelle, l’origine sociale, les capacités physiques ou les croyances religieuses, apparaît dès lors comme un élément fondamental de la réflexion sur l’éthique professionnelle en archéologie. L’exposition « Archéo-Sexisme » présentée ici, initiative conjointe de l’association Archéo-Éthique et de Paye Ta Truelle, est un exemple d’une telle réflexion.

Identification and Characterization of Known Biallelic Mutations in the IFT27 (BBS19) Gene in a Novel Family With Bardet-Biedl Syndrome

Bardet-Biedl syndrome (BBS; MIM 209900) is a rare ciliopathy characterized by retinitis pigmentosa, postaxial polydactyly, obesity, hypogonadism, cognitive impairment and kidney dysfunction. Mutations in 22 BBS genes have been identified to cause the disease. We report a family with typical BBS features (retinitis pigmentosa, postaxial polydactyly, obesity, cognitive impairment, and atrioventricular septal defect) mutated in IFT27/BBS19. IFT27 is part of the Intraflagellar transport (IFT), a bidirectional mechanism allowing the protein motility within the cilia. Using whole exome sequencing, two compound heterozygous mutations were found in the proband (NM_006860.4:c.[104A > G];[349+1G > T], p.[Tyr35Cys];[?]) consistent with the expected autosomal recessive inheritance mode. These two mutations have already been reported but independently in other families and lacking either familial segregation or functional validation. This is the third report of IFT27 mutations in BBS patients confirming IFT27 as a BBS gene (BBS19). Mutations in IFT genes (IFT27, IFT172 and IFT74) confirm the IFT-pathway as a pathomechanism for BBS.

Prenatal diagnosis of focal dermal hypoplasia: Report of three fetuses and review of the literature

Focal dermal hypoplasia (FDH) is a rare syndrome characterized by pleiotropic features knowing to involve mostly skin and limbs. Although FDH has been described in children and adults, the cardinal signs of the fetal phenotype are not straightforward impacting the quality of the prenatal diagnosis. We describe in depth the ultrasound, radiological, macroscopical, and histological phenotype of three female fetuses with a severe form of FDH, propose a review of the literature and an attempt to delineate minimal and cardinal signs for FDH diagnosis. This report confirms the variability of FDH phenotype, highlights unreported FDH features, and allows delineating evocative clinical associations for prenatal diagnosis, namely intrauterine growth retardation, limbs malformations, anterior wall/diaphragm defects, and eye anomalies. © 2016 Wiley Periodicals, Inc.

Sinus node recovery time in the elderly

Measurement of the sinus node recovery time has been proposed as a diagnostic tool for recognition of the sick sinus syndrome. The latter is most frequently encountered in elderly patients with hypertension, coronary heart disease, and atherosclerosis. In order to provide normal values for the sinus node recovery time in this particular population group, atrial pacing studies were carried out in 30 subjects over 50 years of age, all with peripheral vascular disease and some with angina pectoris (10), residua of infarction (6), or hypertension (7). On stimulation, 7 patients maintained a I:I atrioventricular conduction up to the rate of 180/min. Second degree atrioventricular block developed in all other cases. On six occasions, Wenckebach's periods appeared at the relatively slow pacing rate of 120/min. The maximum postoverdrive pause ranged from 680 to 1600 ms with an average of 1100 ms plus or minus 190 (10). For each pacing speed, a correlation was found between the duration of the pause and the control intrinsic cardiac rate, longer pauses being associated with longer resting PP intervals. Beyond 120/min, the duration of the pause was seen to shorten progressively as the driving rate was increased. Finally, the behavior of the sinus node pacemaker following interruption of pacing showed individual variations. After pacing at relatively slow rates, a prompt return to near control values was consistently observed, whereas, after fast rates of driving, a phase of secondary depression developed in about one-half of the studied cases.