Next-generation sequencing for disorders of low and high bone mineral density.

UNLABELLED: To achieve an efficient molecular diagnosis of osteogenesis imperfecta (OI), Ehlers-Danlos syndrome (EDS), and osteopetrosis (OPT), we designed a next-generation sequencing (NGS) platform to sequence 34 genes. We validated this platform on known cases and have successfully identified the causative mutation in most patients without a prior molecular diagnosis. INTRODUCTION: Osteogenesis imperfecta, Ehlers-Danlos syndrome, and osteopetrosis are collectively common inherited skeletal diseases. Evaluation of subjects with these conditions often includes molecular testing which has important counseling and therapeutic and sometimes legal implications. Since several different genes have been implicated in these conditions, Sanger sequencing of each gene can be a prohibitively expensive and time-consuming way to reach a molecular diagnosis. METHODS: In order to circumvent these problems, we have designed and tested a NGS platform that would allow simultaneous sequencing on a single diagnostic platform of different genes implicated in OI, OPT, EDS, and other inherited conditions, leading to low or high bone mineral density. We used a liquid-phase probe library that captures 602 exons (~100 kb) of 34 selected genes and have applied it to test clinical samples from patients with bone disorders. RESULTS: NGS of the captured exons by Illumina HiSeq 2000 resulted in an average coverage of over 900X. The platform was successfully validated by identifying mutations in six patients with known mutations. Moreover, in four patients with OI or OPT without a prior molecular diagnosis, the assay was able to detect the causative mutations. CONCLUSIONS: In conclusion, our NGS panel provides a fast and accurate method to arrive at a molecular diagnosis in most patients with inherited high or low bone mineral density disorders.

Clinical and neuroimaging findings of Cree leukodystrophy: a retrospective case series.

BACKGROUND AND PURPOSE: CLD is a rapidly progressive and invariably fatal neurodegenerative disorder. We describe clinical and neuroimaging findings in 5 infants with CLD. MATERIALS AND METHODS: Retrospective review of medical records of infants with CLD from the past 11 years at our institution was performed. Relevant clinical and demographic data were recorded. Specific attention was directed toward postmortem examination findings and genetic testing. CT and MR imaging results were reviewed. RESULTS: Five Cree infants were diagnosed with CLD. CT demonstrated bilateral symmetric hypoattenuation of the white matter and globus pallidus. MR imaging demonstrated corresponding T2 hyperintensity in these regions and abnormal signal intensity in the thalami and substantia nigra. Symmetric restricted diffusion in the deep white matter was seen. MRS demonstrated decreased NAA, elevated choline, and the presence of lactate. Postmortem examination in 1 infant showed corresponding poor myelination in the brain stem, cerebellum, deep gray structures, and the cerebral hemispheres. Genetic testing in 2 infants revealed homozygous mutations in the eIF2B5 gene. CONCLUSIONS: Neuroimaging in CLD is striking and is an important tool in diagnosing CLD. Extensive white matter involvement as well as involvement of the globus pallidus and patchy involvement of the thalami and substantia nigra are characteristic. MRS findings are compatible with destruction of normal brain parenchyma with evidence of anaerobic metabolism in the regions of demyelination. Clinical suspicion of VWM in a Native American infant from this region should prompt the consideration of CLD with appropriate imaging work-up and genetic testing.

Family history as a predictor of uptake of cancer preventive procedures by women with a BRCA1 or BRCA2 mutation.

Women with a BRCA1 or BRCA2 mutation are at an elevated risk of developing breast and ovarian cancer; however, it is unclear to what extent family history influences the uptake of cancer prevention options. Women with a BRCA1/2 mutation completed a follow-up questionnaire that assessed uptake of cancer preventive options. The pedigree of each woman was reviewed, and information was recorded on cancers diagnosed in relatives. Five hundred and seventeen women were included in the study. Women with a sister with breast cancer were more likely to have a prophylactic mastectomy than those without a sister with breast cancer [odds ratios (OR) = 2.4, p = 0.003]. Uptake of prophylactic mastectomy was significantly lower in women with a mother with ovarian cancer compared with those whose mother did not have ovarian cancer (OR = 0.4, p = 0.01). Having a mother or sister with ovarian cancer significantly predicted the uptake of prophylactic oophorectomy (OR = 1.6, p = 0.04). Women with a BRCA2 mutation were less likely to have a prophylactic oophorectomy than those with a BRCA1 mutation (OR = 0.49, p = 0.0004). Among women with a BRCA1 or BRCA2 mutation, family history predicts the uptake of prophylactic mastectomy and prophylactic oophorectomy.

Peripheral neuropathy in a child with Cree leukodystrophy.

The authors describe peripheral nerve involvement in a 12-month-old boy with Cree leukodystrophy. Nerve conduction and genetic studies were performed during investigation of his leukodystrophy. Mutation analysis of the eukaryotic initiation factor 2B5 gene detected homozygosity of the R195 mutation, confirming the diagnosis of Cree leukodystrophy. Median and posterior tibial motor nerve conduction study results were normal, but sensory responses in the median nerves were unobtainable bilaterally, in keeping with a sensory axonal neuropathy. Somatosensory-evoked potentials were absent in the upper extremities and delayed in the lower extremities, confirming sensory nerve involvement. This degree of sensory nerve involvement has not been previously reported in patients with eukaryotic initiation factor 2B5-related disorders. Peripheral neuropathy should be looked for both clinically and with electrodiagnostic studies in patients with eukaryotic initiation factor 2B-related disorders.

Age at first birth and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers.

An early age at first full-term birth is associated with a reduction in the subsequent development of breast cancer among women in the general population. A similar effect has not yet been reported among women who carry an inherited BRCA1 or BRCA2 mutation. We conducted a matched case-control study on 1816 pairs of women with a BRCA1 (n = 1405) or BRCA2 (n = 411) mutation in an attempt to elucidate the relationship between age at first full-term pregnancy and the risk of developing breast cancer. Information about the age at first childbirth and other pregnancy-related variables was derived from a questionnaire administered to women during the course of genetic counselling. There was no difference in the mean age at first full-term birth in the cases and controls (24.9 years vs. 24.8 years; P = 0.81, respectively). Compared to women whose first child was born at or before 18 years of age, a later age at first full-term birth did not influence the risk of developing breast cancer (OR = 1.00 per year; 95% CI 0.98-1.03; P-trend = 0.67). Stratification by mutation status did not affect the results. These findings suggest that an early first full-term birth does not confer protection against breast cancer in BRCA mutation carriers. Nonetheless, BRCA mutation carriers opting for a prophylactic oophorectomy as a breast and/or ovarian cancer risk-reducing strategy should complete childbearing prior to age 40 when this prevention modality is most effective.

Predictive, pre-natal and diagnostic genetic testing for Huntington's disease: the experience in Canada from 1987 to 2000.

Predictive and pre-natal testing for Huntington's Disease (HD) has been available since 1987. Initially this was offered by linkage analysis, which was surpassed by the advent of the direct mutation test for HD in 1993. Direct mutation analysis provided an accurate test that not only enhanced predictive and pre-natal testing, but also permitted the diagnostic testing of symptomatic individuals. The objective of this study was to investigate the uptake, utilization, and outcome of predictive, pre-natal and diagnostic testing in Canada from 1987 to April 1, 2000. A retrospective design was used; all Canadian medical genetics centres and their affiliated laboratories offering genetic testing for HD were invited to participate. A total of 15 of 22 centres (68.2%), currently offering or ever having offered genetic testing for HD, responded, providing data on test results, demographics, and clinical history. A total of 1061 predictive tests, 15 pre-natal tests, and 626 diagnostic tests were performed. The uptake for predictive testing was approximately 18% of the estimated at-risk Canadian population, ranging from 12.5% in the Maritimes to 20.7% in British Columbia. There appears to have been a decline in the rate of testing in recent years. Of the predictive tests, 45.0% of individuals were found to have an increased risk, and a preponderance of females (60.2%) sought testing. A greater proportion of those at < or = 25% risk sought predictive testing once direct CAG mutation analysis had become available (10.9% after mutation analysis vs 4.7% before mutation analysis, p = 0.0077). Very few pre-natal tests were requested. Of the 15 pre-natal tests, 12 had an increased risk, resulting in termination of pregnancy in all but one. Diagnostic testing identified 68.5% of individuals to be positive by mutation analysis, while 31.5% of those with HD-like symptoms were not found to have the HD mutation. The positive diagnostic tests included 24.5% of individuals with no known prior family history of HD.

Two brothers with severe developmental delay, growth retardation and unusual appearance.

We report on two brothers with short stature, severe developmental delay and unusual appearance. Several conditions including the Russell-Silver, Dubowitz, Floating-Harbour and Cockayne syndromes were considered in the differential diagnosis, but subsequently rejected. These two cases are likely to represent a new autosomal recessive or X-linked recessive syndrome.

Chudley-McCullough syndrome: bilateral sensorineural deafness, hydrocephalus, and other structural brain abnormalities.

The Chudley-McCullough syndrome, an autosomal recessive condition first reported by Chudley et al. [1997], comprises profound sensorineural hearing loss and hydrocephalus secondary to an obstruction of the foramen of Munro. We describe two more sibs with this condition. One girl had sensorineural hearing loss and hydrocephalus due to obstruction of the foramen of Munro. Incidentally she was also found to carry a full mutation in the FMR1 gene. The older sister had profound sensorineural hearing loss and hydrocephalus not due to obstruction of the foramen of Munro; she also had callosal dysgenesis, gray matter heterotopia, cortical dysplasia, and cerebellar dysgenesis. Thus, the Chudley-McCullough syndrome may include hydrocephalus not necessarily related to obstruction of the foramen of Munro and other structural brain abnormalities.

Unusual phenotype in partial trisomy 14.

An 8-year-old boy with partial trisomy 14q and phenotype distinct from previously reported cases is described. The mother carries a balanced 9;14 reciprocal translocation. The patient presented with minor facial anomalies, developmental delay, hyperphagia, and obesity. Imprinting of maternal chromosome 14 or disruption of one or more genes on chromosome 9 may be responsible for our patient's manifestations.

Familial neuroblastoma: report of a kindred with later age at diagnosis.

PURPOSE: To describe the clinical and biologic features of neuroblastoma (NB) in two siblings and their maternal second cousin. PATIENTS AND METHODS: NB was diagnosed in the siblings at 2 1/2 (patient 2) and 5 (patient 3) years of age. NB was diagnosed in their maternal second cousin (patient 1) when she was 7 years old. Standard clinical and biological data, tumor karyotype, and tumor allelotype at select loci were obtained. RESULTS: Patient 1 had International Neuroblastoma Staging System (INSS) stage 4 NB and unfavorable histology but no evidence of MYCN amplification; she died from complications of autologous bone marrow transplantation in second remission. Patient 2 had INSS stage 4 NB with unfavorable histology but no MYCN amplification; her disease recurred 39 months after completing therapy. Patient 3 had INSS stage 1 NB with favorable biologic features; he was treated with surgical excision and remains free of disease. CONCLUSIONS: Familial NB may occur at a later age than predicted by the tumor suppressor gene model of inherited cancer. This report further emphasizes the clinical and biological heterogeneity of familial NB.

SAMS: provisionally unique multiple congenital anomalies syndrome consisting of short stature, auditory canal atresia, mandibular hypoplasia, and skeletal abnormalities.

We report on a young Mennonite child born with short stature, atresia of the external auditory canal, mandibular hypoplasia, and skeletal anomalies. The skeletal defects consist of bilateral humeral hypoplasia, delayed ossification of the pubic rami, and the previously unreported anomaly of humeroscapular synostosis. This girl is the product of a consanguineous mating. This phenotype is unique and does not match that of any previously described condition.

A familial disorder with duodenal atresia and tetralogy of Fallot.

We report on two sibs with tetralogy of Fallot (TOF) and duodenal atresia (DA). The first child, a 6-year-old girl, had a right facial palsy in addition to the TOF and DA. Her brother, age 10 months, was born with bilateral microtia without facial palsy. The children are the product of an apparently non-consanguineous union between clinically normal parents. The pertinent family history includes a paternal aunt with TOF and a cleft lip and palate who died in childhood and another paternal aunt with a supernumerary thumb. This family has anomalies found in several syndromes, but does not meet the diagnostic criteria for any of them. The genetic basis for this condition remains unknown, but the pattern of inheritance is likely either autosomal recessive, or autosomal dominant with variable expression and reduced penetrance. The pathogenesis is unknown, but either a disturbance in neural crest cell migration or familial predisposition to vascular disruption might explain this pattern of malformations.

Mutations in the structural gene for cytochrome c result in deficiency of both cytochromes aa3 and c in Neurospora crassa.

The cyt-12-12 mutant of Neurospora crassa is characterized by slow growth and a deficiency of spectrophotometrically-detectable cytochromes aa3 and c. Using a sib-selection procedure we have isolated the cyt-12+ allele from a cosmid library of N. crassa genomic DNA. Characterization of the cyt-12+ allele reveals that it encodes the structural gene for cytochrome c. DNA sequence analysis of the cyt-12-12 allele revealed a mutation in the cytochrome c coding sequence that results in replacement of a glycine residue, which is invariant in the cytochrome c of other species, with an aspartic acid. Genetic analysis confirms that cyt-12-12 is allelic with the previously-characterized cyc-1-1 mutant, which was also shown to affect the single locus encoding cytochrome c in N. crassa. We suggest that the amount of functional cytochrome c present in mitochondria influences the level of cytochrome aa3.