Hallermann-Streiff Syndrome: No Evidence for a Link to Laminopathies

Hallermann-Streiff syndrome (HSS) is a rare inherited disorder characterized by malformations of the cranium and facial bones, congenital cataracts, microphthalmia, skin atrophy, hypotrichosis, proportionate short stature, teeth abnormalities, and a typical facial appearance with prominent forehead, small pointed nose, and micrognathia. The genetic cause of this developmental disorder is presently unknown. Here we describe 8 new patients with a phenotype of HSS. Individuals with HSS present with clinical features overlapping with some progeroid syndromes that belong to the laminopathies, such as Hutchinson-Gilford progeria syndrome (HGPS) and mandibuloacral dysplasia (MAD). HGPS is caused by de novo point mutations in the LMNA gene, coding for the nuclear lamina proteins lamin A and C. MAD with type A and B lipodystrophy are recessive disorders resulting from mutations in LMNA and ZMPSTE24 , respectively. ZMPSTE24 in addition to ICMT encode proteins involved in posttranslational processing of lamin A. We hypothesized that HSS is an allelic disorder to HGPS and MAD. As the nuclear shape is often irregular in patients with LMNA mutations, we first analyzed the nuclear morphology in skin fibroblasts of patients with HSS, but could not identify any abnormality. Sequencing of the genes LMNA, ZMPSTE24 and ICMT in the 8 patients with HSS revealed the heterozygous missense mutation c.1930C>T (p.R644C) in LMNA in 1 female. Extreme phenotypic diversity and low penetrance have been associated with the p.R644C mutation. In ZMPSTE24 and ICMT , no pathogenic sequence change was detected in patients with HSS. Together, we found no evidence that HSS is another laminopathy

β-Mannosidase deficiency: Heterogeneous manifestation in the first female patient and her brother

Summary β-Mannosidase deficiency was demonstrated in fibroblasts of a girl who showed severe psychomotor retardation, bone deformities and gargoylism and recurrent skin and r

Am. J. Hum. Genet.

Thrombocytopenia–absent radius (TAR) syndrome is characterized by hypomegakaryocytic thrombocytopenia and bilateral radial aplasia in the presence of both thumbs. Other frequent associations are congenital heart disease and a high incidence of cow’s milk intolerance. Evidence for autosomal recessive inheritance comes from families with several affected individuals born to unaffected parents, but several other observations argue for a more complex pattern of inheritance. In this study, we describe a common interstitial microdeletion of 200 kb on chromosome 1q21.1 in all 30 investigated patients with TAR syndrome, detected by microarray-based comparative genomic hybridization. Analysis of the parents revealed that this deletion occurred de novo in 25% of affected individuals. Intriguingly, inheritance of the deletion along the maternal line as well as the paternal line was observed. The absence of this deletion in a cohort of control individuals argues for a specific role played by the microdeletion in the pathogenesis of TAR syndrome. We hypothesize that TAR syndrome is associated with a deletion on chromosome 1q21.1 but that the phenotype develops only in the presence of an additional as-yet-unknown modifier (mTAR)

Variations in the NBN/NBS1 gene and the risk of breast cancer in non-BRCA1/2 French Canadian families with high risk of breast cancer

<p>Abstract</p> <p>Background</p> <p>The Nijmegen Breakage Syndrome is a chromosomal instability disorder characterized by microcephaly, growth retardation, immunodeficiency, and increased frequency of cancers. Familial studies on relatives of these patients indicated that they also appear to be at increased risk of cancer.</p> <p>Methods</p> <p>In a candidate gene study aiming at identifying genetic determinants of breast cancer susceptibility, we undertook the full sequencing of the <it>NBN </it>gene in our cohort of 97 high-risk non-<it>BRCA1 </it>and -<it>BRCA2 </it>breast cancer families, along with 74 healthy unrelated controls, also from the French Canadian population. <it>In silico </it>programs (ESEfinder, NNSplice, Splice Site Finder and MatInspector) were used to assess the putative impact of the variants identified. The effect of the promoter variant was further studied by luciferase gene reporter assay in MCF-7, HEK293, HeLa and LNCaP cell lines.</p> <p>Results</p> <p>Twenty-four variants were identified in our case series and their frequency was further evaluated in healthy controls. The potentially deleterious p.Ile171Val variant was observed in one case only. The p.Arg215Trp variant, suggested to impair NBN binding to histone γ-H2AX, was observed in one breast cancer case and one healthy control. A promoter variant c.-242-110delAGTA displayed a significant variation in frequency between both sample sets. Luciferase reporter gene assay of the promoter construct bearing this variant did not suggest a variation of expression in the MCF-7 breast cancer cell line, but indicated a reduction of luciferase expression in both the HEK293 and LNCaP cell lines.</p> <p>Conclusion</p> <p>Our analysis of <it>NBN </it>sequence variations indicated that potential <it>NBN </it>alterations are present, albeit at a low frequency, in our cohort of high-risk breast cancer cases. Further analyses will be needed to fully ascertain the exact impact of those variants on breast cancer susceptibility, in particular for variants located in <it>NBN </it>promoter region.</p

The Slavic NBN founder mutation: a role for reproductive fitness?

The vast majority of patients with Nijmegen Breakage Syndrome (NBS) are of Slavic origin and carry a deleterious deletion (c.657del5; rs587776650) in the NBN gene on chromosome 8q21. This mutation is essentially confined to Slavic populations and may thus be considered a Slavic founder mutation. Notably, not a single parenthood of a homozygous c.657del5 carrier has been reported to date, while heterozygous carriers do reproduce but have an increased cancer risk. These observations seem to conflict with the considerable carrier frequency of c.657del5 of 0.5% to 1% as observed in different Slavic populations because deleterious mutations would be eliminated quite rapidly by purifying selection. Therefore, we propose that heterozygous c.657del5 carriers have increased reproductive success, i.e., that the mutation confers heterozygote advantage. In fact, in our cohort study of the reproductive history of 24 NBS pedigrees from the Czech Republic, we observed that female carriers gave birth to more children on average than female non-carriers, while no such reproductive differences were observed for males. We also estimate that c.657del5 likely occurred less than 300 generations ago, thus supporting the view that the original mutation predated the historic split and subsequent spread of the 'Slavic people'. We surmise that the higher fertility of female c.657del5 carriers reflects a lower miscarriage rate in these women, thereby reflecting the role of the NBN gene product, nibrin, in the repair of DNA double strand breaks and their processing in immune gene rearrangements, telomere maintenance, and meiotic recombination, akin to the previously described role of the DNA repair genes BRCA1 and BRCA2

Cobblestone-like brain dysgenesis and altered glycosylation in congenital cutis laxa. Debre type

Objective: To delineate a new syndrome of brain dysgenesis and cutis laxa based on the description of 11 patients belonging to nine unrelated families recruited through an international collaboration effort. Methods: Careful clinical assessment of patients from birth to the age of 23 years with follow-up studies ranging from 3 to 20 years. Biochemical studies of serum proteins glycosylation by isoelectric focusing and capillary zone electrophoresis were performed in 10 patients. Brain MRI studies using conventional methods were analyzed in eight patients. Results: An expanded clinical spectrum of a syndrome comprising facial dysmorphia (enlarged anterior fontanelles, downward slant of palpebral fissures, prominent root of the nose), a connective tissue disorder (inguinal hernia, hip dislocation, high myopia), and neurologic impairment was defined. Early developmental delay was followed by onset of generalized seizures by the end of the first decade and a subsequent neurodegenerative course. A defect of N- or N- plus O-glycosylation of serum transferrins and ApoCIII was observed in 10 patients. An unusual cobblestone-like cortical malformation over the frontal and parietal regions was seen in eight patients and cerebellar abnormalities, including two patients with Dandy-Walker malformation, were observed in three patients. Conclusions: Our results suggest that autosomal recessive cutis laxa, Debré type, initially considered a dermatologic syndrome, is a multisystemic disorder with cobblestone-like brain dysgenesis manifesting as developmental delay and an epileptic neurodegenerative syndrome. It might represent a metabolic cause of Dandy-Walker malformation. It is associated with a deficient N- and-O glycosylation of proteins and shares many similarities with muscle-eye-brain syndromes