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ObjectiveTo test the hypothesis that de novo genetic variants are responsible for moyamoya disease (MMD) in children with unaffected relatives, we performed exome sequencing of 28 affected children and their unaffected parents.MethodsExome sequencing was performed on 28 trios of affected patients with MMD and unaffected parents.ResultsWe identified 3 novel rare de novo RNF213 variants, 1 in the RING domain and 2 in a highly conserved region distal to the RING domain (4,114–4,120). These de novo cases of MMD present at a young age with aggressive MMD and uniquely have additional occlusive vascular lesions, including renal artery stenosis. Two previously reported cases had de novo variants in the same limited region and presented young with aggressive MMD, and 1 case had narrowing of the inferior abdominal aorta.ConclusionsThese results indicate a novel syndrome associated with RNF213 rare variants defined by de novo mutations disrupting highly conserved amino acids in the RING domain and a discrete region distal to the RING domain delimited by amino acids 4,114 to 4,120 leading to onset of severe MMD before 3 years of age and occlusion of other arteries, including the abdominal aorta, renal, iliac, and femoral arteries.

Hereditary biallelic mismatch repair deficiency (BMMRD) is caused by biallelic mutations in the mismatch repair (MMR) genes and manifests features of neurofibromatosis type 1, gastrointestinal (GI) polyposis, and GI, brain, and hematological cancers. This is the first study to characterize the GI phenotype in BMMRD using both retrospective and prospective surveillance data.The International BMMRD Consortium was created to collect information on BMMRD families referred from around the world. All patients had germline biallelic MMR mutations or lack of MMR protein staining in normal and tumor tissue. GI screening data were obtained through medical records with annual updates.Thirty-five individuals from seven countries were identified with BMMRD. GI data were available on 24 of 33 individuals (73%) of screening age, totaling 53 person-years. The youngest age of colonic adenomas was 7, and small bowel adenoma was 11. Eight patients had 19 colorectal adenocarcinomas (CRC; median age 16.7 years, range 8-25), and 11 of 18 (61%) CRC were distal to the splenic flexure. Eleven patients had 15 colorectal surgeries (median 14 years, range 9-25). Four patients had five small bowel adenocarcinomas (SBC; median 18 years, range 11-33). Two CRC and two SBC were detected during surveillance within 6-11 months and 9-16 months, respectively, of last consecutive endoscopy. No patient undergoing surveillance died of a GI malignancy. Familial clustering of GI cancer was observed.The prevalence and penetrance of GI neoplasia in children with BMMRD is high, with rapid development of carcinoma. Colorectal and small bowel surveillance should commence at ages 3-5 and 8 years, respectively.

Meier-Gorlin syndrome is a rare autosomal recessive genetic condition whose primary clinical hallmarks include small stature, small external ears and small or absent patellae. Using marker-assisted mapping in multiple families from a founder population and traditional coding exon sequencing of positional candidate genes, we identified three different mutations in the gene encoding ORC4, a component of the eukaryotic origin recognition complex, in five individuals with Meier-Gorlin syndrome. In two such individuals that were negative for mutations in ORC4, we found potential mutations in ORC1 and CDT1, two other genes involved in origin recognition. ORC4 is well conserved in eukaryotes, and the yeast equivalent of the human ORC4 missense mutation was shown to be pathogenic in functional assays of cell growth. This is the first report, to our knowledge, of a germline mutation in any gene of the origin recognition complex in a vertebrate organism.

Autosomal-recessive cutis laxa type 2 (ARCL2) is a multisystem disorder characterized by the appearance of premature aging, wrinkled and lax skin, joint laxity, and a general developmental delay. Cutis laxa includes a family of clinically overlapping conditions with confusing nomenclature, generally requiring molecular analyses for definitive diagnosis. Six genes are currently known to mutate to yield one of these related conditions. We ascertained a cohort of typical ARCL2 patients from a subpopulation isolate within eastern Canada. Homozygosity mapping with high-density SNP genotyping excluded all six known genes, and instead identified a single homozygous region near the telomere of chromosome 17, shared identically by state by all genotyped affected individuals from the families. A putative pathogenic variant was identified by direct DNA sequencing of genes within the region. The single nucleotide change leads to a missense mutation adjacent to a splice junction in the gene encoding pyrroline-5-carboxylate reductase 1 (PYCR1). Bioinformatic analysis predicted a pathogenic effect of the variant on splice donor site function. Skipping of the associated exon was confirmed in RNA from blood lymphocytes of affected homozygotes and heterozygous mutation carriers. Exon skipping leads to deletion of the reductase functional domain-coding region and an obligatory downstream frameshift. PYCR1 plays a critical role in proline biosynthesis. Pathogenicity of the genetic variant in PYCR1 is likely, given that a similar clinical phenotype has been documented for mutation carriers of another proline biosynthetic enzyme, pyrroline-5-carboxylate synthase. Our results support a significant role for proline in normal development.

Family physicians (FPs) are increasingly involved in delivering genetic services. Familiarization with aspects of genetic counseling may enable FPs to help patients make informed choices. Exploration of interactive role-play as a means to raise FPs’ awareness of the process and content of genetic counseling. FPs attending two large Canadian family medicine conferences in 2005 were eligible—93 participated. FPs discussed a case during a one-on-one session with a genetic counselor. Evaluation involved pre and post intervention questionnaires FPs’ baseline genetic knowledge was self-rated as uniformly poor. Baseline confidence was highest in eliciting family history and providing psychosocial support and lowest in discussing risks/benefits of genetic testing and counseling process. Post-intervention, 80% of FPs had better appreciation of family history and 97% indicated this was an effective learning experience. Role-play with FPs is effective in raising awareness of the process and content of genetic counseling and may be applied to other health disciplines.

Gastric cancer is among the leading causes of cancer-related deaths worldwide. While heritable forms of gastric cancer are relatively rare, identifying the genes responsible for such cases can inform diagnosis and treatment for both hereditary and sporadic cases of gastric cancer. Mutations in the E-cadherin gene, CDH1, account for 40% of the most common form of familial gastric cancer (FGC), hereditary diffuse gastric cancer (HDGC). The genes responsible for the remaining forms of FGC are currently unknown. Here we examined a large family from Maritime Canada with FGC without CDH1 mutations, and identified a germline coding variant (p.P946L) in mitogen-activated protein kinase kinase kinase 6 (MAP3K6). Based on conservation, predicted pathogenicity and a known role of the gene in cancer predisposition, MAP3K6 was considered a strong candidate and was investigated further. Screening of an additional 115 unrelated individuals with non-CDH1 FGC identified the p.P946L MAP3K6 variant, as well as four additional coding variants in MAP3K6 (p.F849Sfs*142, p.P958T, p.D200Y and p.V207G). A somatic second-hit variant (p.H506Y) was present in DNA obtained from one of the tumor specimens, and evidence of DNA hypermethylation within the MAP3K6 gene was observed in DNA from the tumor of another affected individual. These findings, together with previous evidence from mouse models that MAP3K6 acts as a tumor suppressor, and studies showing the presence of somatic mutations in MAP3K6 in non-hereditary gastric cancers and gastric cancer cell lines, point towards MAP3K6 variants as a predisposing factor for FGC., Author Summary The underlying genetic mutations involved in 60% of inherited gastric cancer cases remain unknown. Here we present a large, extended pedigree with familial gastric cancer and an association in part of the family with a mutation in MAP3K6. The conservation, predicted pathogenicity of the variant, tissue distribution, and known function of MAP3K6 made this a strong candidate that warranted further investigation. Examination of an additional 115 unrelated probands identified additional mutations in MAP3K6, including a truncating mutation.

A syndrome associated with 19q13.11 microdeletions has been proposed based on seven previous cases that displayed developmental delay, intellectual disability, speech disturbances, pre- and post-natal growth retardation, microcephaly, ectodermal dysplasia, and genital malformations in males. A 324-kb critical region was previously identified as the smallest region of overlap (SRO) for this syndrome. To further characterize this microdeletion syndrome, we present five patients with deletions within 19q12q13.12 identified using a whole-genome oligonucleotide microarray. Patients 1 and 2 possess deletions overlapping the SRO, and Patients 3–5 have deletions proximal to the SRO. Patients 1 and 2 share significant phenotypic overlap with previously reported cases, providing further definition of the 19q13.11 microdeletion syndrome phenotype, including the first presentation of ectrodactyly in the syndrome. Patients 3–5, whose features include developmental delay, growth retardation, and feeding problems, support the presence of dosage-sensitive genes outside the SRO that may contribute to the abnormal phenotypes observed in this syndrome. Multiple genotype–phenotype correlations outside the SRO are explored, including further validation of the deletion of WTIP as a candidate for male hypospadias observed in this syndrome. We postulate that unique patient-specific deletions within 19q12q13.1 may explain the phenotypic variability observed in this emerging contiguous gene deletion syndrome. © 2013 Wiley Periodicals, Inc.

Item does not contain fulltext Environmental manganese (Mn) toxicity causes an extrapyramidal, parkinsonian-type movement disorder with characteristic magnetic resonance images of Mn accumulation in the basal ganglia. We have recently reported a suspected autosomal recessively inherited syndrome of hepatic cirrhosis, dystonia, polycythemia, and hypermanganesemia in cases without environmental Mn exposure. Whole-genome mapping of two consanguineous families identified SLC30A10 as the affected gene in this inherited type of hypermanganesemia. This gene was subsequently sequenced in eight families, and homozygous sequence changes were identified in all affected individuals. The function of the wild-type protein and the effect of sequence changes were studied in the manganese-sensitive yeast strain Deltapmr1. Expressing human wild-type SLC30A10 in the Deltapmr1 yeast strain rescued growth in high Mn conditions, confirming its role in Mn transport. The presence of missense (c.266T>C [p.Leu89Pro]) and nonsense (c.585del [p.Thr196Profs( *)17]) mutations in SLC30A10 failed to restore Mn resistance. Previously, SLC30A10 had been presumed to be a zinc transporter. However, this work has confirmed that SLC30A10 functions as a Mn transporter in humans that, when defective, causes Mn accumulation in liver and brain. This is an important step toward understanding Mn transport and its role in neurodegenerative processes.

Charcot-Marie-Tooth disease (CMT) represents a family of related sensorimotor neuropathies. We studied a large family from a rural eastern Canadian community, with multiple individuals suffering from a condition clinically most similar to autosomal recessive axonal CMT, or AR-CMT2. Homozygosity mapping with high-density SNP genotyping of six affected individuals from the family excluded 23 known genes for various subtypes of CMT and instead identified a single homozygous region on chromosome 9, at 122,423,730–129,841,977 Mbp, shared identical by state in all six affected individuals. A homozygous pathogenic variant was identified in the gene encoding leucine rich repeat and sterile alpha motif 1 (LRSAM1) by direct DNA sequencing of genes within the region in affected DNA samples. The single nucleotide change mutates an intronic consensus acceptor splicing site from AG to AA. Direct analysis of RNA from patient blood demonstrated aberrant splicing of the affected exon, causing an obligatory frameshift and premature truncation of the protein. Western blotting of immortalized cells from a homozygous patient showed complete absence of detectable protein, consistent with the splice site defect. LRSAM1 plays a role in membrane vesicle fusion during viral maturation and for proper adhesion of neuronal cells in culture. Other ubiquitin ligases play documented roles in neurodegenerative diseases. LRSAM1 is a strong candidate for the causal gene for the genetic disorder in our kindred., Author Summary Sensory motor neuropathies are diseases of the peripheral nervous system, involving primarily the nerves which control our muscles. These can result from either genetic or non-genetic causes, with genetic causes usually referred to as Charcot-Marie-Tooth (CMT) disease after the three clinicians who first described the key diagnostic markers. CMT patients lose muscle function, mainly in their arms and legs, with increasing severity during their lives. There are almost two dozen known genes that can mutate to cause CMT, and these fall into a wide variety of biochemical cellular pathways. We identified a group of patients with CMT from a small rural community, with good reason to suspect a genetic basis for their disease. Using high-throughput mapping and DNA sequencing technologies developed as part of the Human Genome Project, we were able to find the likely mutated gene, which was not any of the previously known CMT genes. Based on its sequence, the gene, called LRSAM1, probably plays a role in the correct metabolism of other proteins in the cell. Among the known CMT genes, some are also involved in protein metabolism, suggesting that this is a generally important pathway in the neurons that control muscle activity.