8.5 Mb deletion at distal 5p in a male ascertained for azoospermia

Mate-pair genome sequencing reveals structural variants for idiopathic male infertility

Currently, routine genetic investigation for male infertility includes karyotyping analysis and PCR for Y chromosomal microdeletions to provide prognostic information such as sperm retrieval success rate. However, over 85% of male infertility remain idiopathic. We assessed 101 male patients with primary infertility in a retrospective cohort analysis who have previously received negative results from standard-of-care tests. Mate-pair genome sequencing (large-insert size library), an alternative long-DNA sequencing method, was performed to detect clinically significant structural variants (SVs) and copy-number neutral absence of heterozygosity (AOH). Candidate SVs were filtered against our in-house cohort of 1077 fertile men. Genes disrupted by potentially clinically significant variants were correlated with single-cell gene expression profiles of human fetal and postnatal testicular developmental lineages and adult germ cells. Follow-up studies were conducted for each patient with clinically relevant finding(s). Molecular diagnoses were made in 11.1% (7/63) of patients with non-obstructive azoospermia and 13.2% (5/38) of patients with severe oligozoospermia. Among them, 12 clinically significant SVs were identified in 12 cases, including five known syndromes, one inversion, and six SVs with direct disruption of genes by intragenic rearrangements or complex insertions. Importantly, a genetic defect related to intracytoplasmic sperm injection (ICSI) failure was identified in a patient with non-obstructive azoospermia, illustrating the additional value of an etiologic diagnosis in addition to determining sperm retrieval rate. Our study reveals a landscape of various genomic variants in 101 males with idiopathic infertility, not only advancing understanding of the underlying mechanisms of male infertility, but also impacting clinical management.

Three Offspring with Cri-du-Chat Syndrome from Phenotypically Normal Parents

Cri-du-chat syndrome is characterized by facial dysmorphism, intellectual disability, and multiple congenital anomalies. Most cases occur de novo. Here, we report 3 siblings with cri-du-chat syndrome born to healthy parents. The proband was admitted to our clinic at the age of 6.5 years due to severe intellectual disability, facial dysmorphism, and heart defect. His karyotype showed a deletion of chromosome 5p. Microarray analysis revealed a 29-Mb deletion in chromosome 5p and a 4.7-Mb duplication in chromosome 19q. FISH analysis indicated an unbalanced translocation between 5p13.3 and 19q13.4. During follow-up, the second and the third child of the family were born with the same chromosome abnormality. Parental peripheral blood and skin fibroblast karyotypes as well as the FISH results using chromosome 5p- and 19q-specific subtelomeric probes were normal. FISH analysis of the father's sperm detected a 5p deletion in 12.8% of 200 cells, and microarray analysis confirmed the same unbalanced chromosome abnormality in a mosaic pattern. Uncultured peripheral blood and buccal smear of the father were also studied by FISH to exclude low-level mosaicism and in vitro culture effect. This is the first study that provides molecular evidence of paternal gonadal mosaicism of an unbalanced translocation detected in 3 siblings with cri-du-chat syndrome.

Multigenerational autosomal dominant inheritance of 5p chromosomal deletions

Deletion of the short arm of chromosome 5 (5p-) is associated with phenotypic features including a cat-like cry in infancy, dysmorphic facial features, microcephaly, and intellectual disability, and when encompassing a minimal critical region, may be defined as Cri-du-Chat syndrome (CdCS). Most 5p deletions are de novo in origin, and familial cases are often associated with translocation and inversion. Herein, we report three multigenerational families carrying 5p terminal deletions of different size transmitted in an autosomal dominant manner causing variable clinical findings. Terminal 5p deletions and the mode of inheritance were clinically characterized and molecularly analyzed by a combination of microarray and fluorescence in situ hybridization analyses. Shared phenotypic features documented in this cohort included neuropsychiatric findings, poor growth, and dysmorphic facial features. This study supports newly recognized effects of aberrant SEMA5A and CTNND2 dosage on severity of autistic and cognitive phenotypes. Comparative analysis of the breakpoints narrows the critical region for the cat-like cry down to an interval less than 1 Mb encompassing a candidate gene ICE1, which regulates small nuclear RNA transcription. This study also indicates that familial terminal 5p deletion is a rare presentation displaying intra- and inter-familial phenotypic variability, the latter of which may be attributed to size and gene content of the deletion. The observed intra-familial phenotypic heterogeneity suggests that additional modifying elements including genetic and environmental factors may have an impact on the clinical manifestations observed in 5p deletion carriers, and in time, further high resolution studies of 5p deletion breakpoints will continue to aid in defining genotype-phenotype correlations.

A cryptic balanced translocation (5;17), a puzzle revealed through a critical evaluation of the pedigree and a FISH focused on candidate loci suggested by the phenotype

We report a case of a woman with a cryptic balanced translocation between chromosomes 5 and 17, suspected during genetic counseling. The woman had a history of previous fetal losses attributed to lissencephaly and intra uterine growth retardation (IUGR) and a daughter with dysmorphic features and mental retardation, previously attributed to a small deletion 5pter, detected years ago by a first generation CGH-array. This peculiar combination of personal and family history suggested the opportunity to carry out a FISH approach, focusing on chromosomes 5 and 17, based on the idea that a malsegregation secondary to a balanced translocation, might have escaped the first CGH array. This approach allowed the identification of a balanced translocation in the mother, FISH in the affected child confirmed the partial 5p deletion predicted by the previous CGH array and identified a new 17p duplication that had not been detected before. The described translocation opens the possibility of alternative imbalances that were probably responsible for previous fetal losses. The imbalances were confirmed by a new high resolution SNP array. We conclude that despite the availability of highly effective and sensitive genomic approaches a careful evaluation of medical history is highly recommended since it can suggest clinical hypothesis that can be confirmed by more classical and molecular cytogenetic based approaches.

A three-generation family with terminal microdeletion involving 5p15.33-32 due to a whole-arm 5;15 chromosomal translocation with a steady phenotype of atypical cri du chat syndrome

Cri du chat syndrome is characterized by cat-like cry, facial dysmorphisms, microcephaly, speech delay, intellectual disability and slow growth rate, which are present with variable frequency. The typical cri du chat syndrome, due to 5p15.2 deletion, includes severe intellectual disability, facial dysmorphisms, neonatal hypotonia and pre- and post-natal growth retardation, whereas more distal deletions in 5p15.3 lead to cat-like cry and speech delay and produce the clinical picture of the atypical cri du chat syndrome, with minimal or absent intellectual impairment. In this article we report a three-generation family with an unbalanced whole arm translocation between chromosome 5 and 15 and a microdeletion of 5.5 Mb involving 5p15.33-32. By reporting the smallest terminal deletion of 5p15.3 described so far and by reviewing the literature we discuss the genotype/phenotype correlations of the distal region of the cri du chat syndrome. The previously described critical region for the speech delay may be narrowed down and microcephaly, growth retardation and dysmorphic facial features can be included in the phenotypic expression of the atypical cri du chat syndrome due to 5p15.3 deletions.

A new case of rob(14;17) in cattle

Robertsonian translocations, also called centric fusions, represent the most frequent chromosome anomalies in cattle, and rob(1;29) is the most widespread. However, centric fusions involving other chromosomes have been discovered in different cattle breeds. Here we report the appearance of a new case of rob(14;17) in an Italian cattle breed more than ten years after the first and only case had been observed, and we demonstrate the independent origin of this anomaly from the previous case.

Cri du Chat syndrome

The Cri du Chat syndrome (CdCS) is a genetic disease resulting from a deletion of variable size occurring on the short arm of chromosome 5 (5p-). The incidence ranges from 1:15,000 to 1:50,000 live-born infants. The main clinical features are a high-pitched monochromatic cry, microcephaly, broad nasal bridge, epicanthal folds, micrognathia, abnormal dermatoglyphics, and severe psychomotor and mental retardation. Malformations, although not very frequent, may be present: cardiac, neurological and renal abnormalities, preauricular tags, syndactyly, hypospadias, and cryptorchidism. Molecular cytogenetic analysis has allowed a cytogenetic and phenotypic map of 5p to be defined, even if results from the studies reported up to now are not completely in agreement. Genotype-phenotype correlation studies showed a clinical and cytogenetic variability. The identification of phenotypic subsets associated with a specific size and type of deletion is of diagnostic and prognostic relevance. Specific growth and psychomotor development charts have been established. Two genes, Semaphorin F (SEMAF) and delta-catenin (CTNND2), which have been mapped to the "critical regions", are potentially involved in cerebral development and their deletion may be associated with mental retardation in CdCS patients. Deletion of the telomerase reverse transcriptase (hTERT) gene, localised to 5p15.33, could contribute to the phenotypic changes in CdCS. The critical regions were recently refined by using array comparative genomic hybridisation. The cat-like cry critical region was further narrowed using quantitative polymerase chain reaction (PCR) and three candidate genes were characterised in this region. The diagnosis is based on typical clinical manifestations. Karyotype analysis and, in doubtful cases, FISH analysis will confirm the diagnosis. There is no specific therapy for CdCS but early rehabilitative and educational interventions improve the prognosis and considerable progress has been made in the social adjustment of CdCS patients.

The natural history of Cri du Chat Syndrome. A report from the Italian Register

The aim of this report is to provide an update on the natural history of the Cri du Chat Syndrome by means of the Italian Register (I.R.). Two hundred twenty patients were diagnosed by standard cytogenetic methods and 112 of these were also characterised by molecular-cytogenetic investigation (FISH). FISH analysis showed interstitial deletions, short terminal deletions and other rare rearrangements not previously correctly diagnosed by standard cytogenetics. The diagnosis was made in the first month of life in 42% and within first year in 82% of cases. The remaining 18% were diagnosed at an age ranging from 13 months to 47 years. At the last follow-up, patient age ranged from 8 months to 61 years. Mortality, already low, has decreased over time as it is lower between 1984-2002 compared to 1965-1983. Mortality was higher in patients with unbalanced translocations resulting in 5p deletions. Our data confirm that the cat-like cry and peculiar timbre of voice are the most typical signs of the syndrome, not only at birth but also later and these are the only signs which might suggest the diagnosis in patients with small deletions and mild clinical picture. A cytogenetic and clinical variability must be underlined. Cardiac, cerebral, renal and gastrointestinal malformations were more frequent in the patients with unbalanced translocations resulting in 5p deletions. Sucking and feeding difficulties and respiratory infections are frequent in the first months or years of life. Intubation difficulties linked to larynx anomalies must be considered. Psychomotor development is delayed in all patients but there is a variability related to deletion size and type as well as other genetic and environmental factors. However, the results showed an improvement in the acquisition of the development skills and progress in social introduction which should encourage caregivers and parents to work together in carrying out the rehabilitative and educational interventions.