Mutation of FA2H underlies a complicated form of hereditary spastic paraplegia (SPG35).

Hereditary spastic paraplegia (HSP) describes a heterogeneous group of inherited neurodegenerative disorders in which the cardinal pathological feature is upper motor neurone degeneration leading to progressive spasticity and weakness of the lower limbs. Using samples from a large Omani family we recently mapped a gene for a novel autosomal recessive form of HSP (SPG35) in which the spastic paraplegia was associated with intellectual disability and seizures. Magnetic resonance imaging of the brain of SPG35 patients showed white matter abnormalities suggestive of a leukodystrophy. Here we report homozygous mutations in the fatty acid 2-hydroxylase gene (FA2H) in the original family used to define the SPG35 locus (p.Arg235Cys) as well as in a previously unreported Pakistani family with a similar phenotype (p.Arg53_Ile58del). Measurement of enzyme activity in vitro revealed significantly reduced enzymatic function of FA2H associated with these mutations. These results demonstrate that mutations in FA2H are associated with SPG35, and that abnormal hydroxylation of myelin galactocerebroside lipid components can lead to a severe progressive phenotype, with a clinical presentation of complicated HSP and radiological features of leukodystrophy. (c) 2010 Wiley-Liss, Inc.

Clinically-Defined Maturity Onset Diabetes of the Young in Omanis: Absence of the common Caucasian gene mutations.

OBJECTIVES: We are seeing a progressive increase in the number of young patients with clinically defined maturity onset diabetes of the young (MODY) having a family history suggestive of a monogenic cause of their disease and no evidence of autoimmune type 1 diabetes mellitus (T1DM). The aim of this study was to determine whether or not mutations in the 3 commonest forms of MODY, hepatic nuclear factor 4α (HNF4α), HNF1α and glucokinase (GK), are a cause of diabetes in young Omanis. METHODS: The study was performed at Sultan Qaboos University Hospital (SQUH), Oman. Twenty young diabetics with a family history suggestive of monogenic inheritance were identified in less than 18 months; the median age of onset of diabetes was 25 years and the median body mass index (BMI) 29 at presentation. Screening for the presence of autoimmune antibodies against pancreatic beta cells islet cell antibody (ICA) and glutamic acid decarboxylase (GAD) was negative. Fourteen of them consented to genetic screening and their blood was sent to Prof. A. Hattersley's Unit at the Peninsular Medical School, Exeter, UK. There, their DNA was screened for known mutations by sequencing exon 1-10 of the GCK and exon 2-10 of the HNF1α and HNF4α genes, the three commonest forms of MODY in Europe. RESULTS: Surprisingly, none of the patients had any of the tested MODY mutations. CONCLUSION: In this small sample of patients with clinically defined MODY, mutations of the three most commonly affected genes occurring in Caucasians were not observed. Either these patients have novel MODY mutations or have inherited a high proportion of the type 2 diabetes mellitus (T2DM) susceptibility genes compounded by excessive insulin resistance due to obesity.

Molecular analysis of CYP1B1 in Omani patients with primary congenital glaucoma: a pilot study.

PURPOSE: To screen cytochrome P4501B1 (CYP1B1) for causative mutations in Omani patients with a clinical diagnosis of primary congenital glaucoma (PCG) METHODS: Nine PCG families were recruited for the study. All patients underwent detailed clinical examinations to confirm the diagnosis of PCG. The families of index patients were also examined. Genealogical information was obtained by pedigree analysis. The primary candidate gene, CYP1B1, was amplified from genomic DNA, sequenced, and analyzed in patients to identify the disease-causing mutations. RESULTS: Eight of the nine PCG families were consanguineous (89%). Molecular analysis of CYP1B1 showed three distinct mutations, p.G61E, p.D374N, and p.R368H, in seven of nine unrelated PCG index patients (78%). Six patients had homozygous mutations and one had a compound heterozygous mutation. Causative mutations were not identified in two families. In family 4, the index patient was found to be heterozygous for the p.E229K variant. In family 6, although affected individuals were found to be homozygous in the CYP1B1 region, no mutation could be identified. CONCLUSIONS: This study indicates that CYP1B1 could be the predominant cause of PCG in the Omani population (78%). Omani PCG patients show allelic heterogeneity. Further studies are needed to delineate the spectrum of CYP1B1mutations in Omani PCG families and to identify new or modifier genes contributing to the manifestations of PCG in this region.

Impact of BRAF, MLH1 on the incidence of microsatellite instability high colorectal cancer in populations based study.

We have identified an alternative pathway of tumorigenesis in sporadic colon cancer, involving microsatellite instability due to mismatched repair methylation, which may be driven by mutations in the BRAF gene (V600E). Colorectal cancer (CRC) is the most common cancer in the world, and African Americans show a higher incidence than other populations in the United States. We analyzed sporadic CRCs in Omani (of African origin, N = 61), Iranian (of Caucasian origin, N = 53) and African American (N = 95) patients for microsatellite instability, expression status of mismatched repair genes (hMLH1, hMSH2) and presence of the BRAF (V600E) mutation. In the Omani group, all tumors with BRAF mutations were located in the left side of the colon, and for African Americans, 88% 7 of tumors with BRAF mutations were found in the right side of the colon. In African Americans, 31% of tumors displayed microsatellite instability at two or more markers (MSI-H), while this rate was 26% and 13% for tumors in the Iranian and Omani groups, respectively. A majority of these MSI-H tumors were located in the proximal colon (right side) in African American and Iranian subjects, whereas most were located in the distal colon (left side) in Omani subjects. Defects in hMLH1 gene expression were found in 77% of MSI-H tumors in both African Americans and Iranians and in 38% of tumors in Omanis. BRAF mutations were observed in all subjects: 10% of tumors in African Americans (8/82), 2% of tumors in Iranians (1/53), and 19% of tumors in Omanis (11/59). Our findings suggest that CRC occurs at a younger age in Omani and Iranian patients, and these groups showed a lower occurrence of MSI-H than did African American patients. Our multivariate model suggests an important and significant role of hMLH1 expression and BRAF mutation in MSI-H CRC in these populations. The high occurrence of MSI-H tumors in African Americans may have significant implications for treatment, since patients with MSI-H lesions display a different response to chemotherapeutic agents such as 5-fluorouracil.

Sporadic colon cancer: mismatch repair immunohistochemistry and microsatellite instability in Omani subjects.

BACKGROUND: Colorectal carcinoma (CRC) is the most common gastrointestinal malignancy in the world, and there are suggestions of a particularly high incidence in the Middle East, including those of African origin. Defects in DNA mismatch repair (MMR) systems are involved in the carcinogenesis of both sporadic and inherited human cancers. We assessed colonic cancers in an attempt to identify tumors with DNA MMR deficiency and microsatellite instability (MSI). Additionally, we tested the ability of cell cycle regulator p16 that effects cell proliferation and can be abrogated by hypermethylation of the promoter region. METHODS: We reviewed the charts of 756 patients who were referred to the Oman major colonoscopy unit of the Sultan Qaboos University Hospital and Royal Hospital from the years 2000 to 2004. Colon cancer tissue was assayed using immunohistochemistry for expression of hMLH1 and hMSH2, and a panel of five pairs of microsatellite primers (NR21, NR22, NR24, BAT25, and BAT26) for MSI-H analysis and additional dinucleotide markers (D17S250, D5S346, and D2S123) used for MSI-L. The expression status of MMR genes and MSI was correlated with cancer stage, location, and histology. A total of 49 tumors were analyzed for histopathology, MSI, and hMLH1/hMSH2 protein expression analysis. The methylation status of the p16 promoter was determined by methylation-specific polymerase chain reaction (PCR). RESULTS: The mean age for the carcinomas was 52.2 years and 53% of the patients were male. The majority of the tumors were left-sided. The information currently available indicates that there is an incidence of 4.7% colon cancer (49/1036) and 12.1% (126/1290) colon adenoma among the cases who underwent colonoscopy at these centers. The rate of MSI-H was 12.2% (n = 6), which appears to be the same as previously reported in literature. Eight of 49 tumors (16.3%) were MMR defective by IHC. Defects in the mismatch repair genes hMLH1 and hMSH2 were found in four (66.7%) and two (33.3%) of CRCs MSI-H cases, respectively. Defects in hMLH1 expression in tumors were commonly associated with moderate differentiation. The p16 promoter was methylated in 4% of tumors. CONCLUSION: This is the first genetic study of CRC in this region of the world to demonstrate the incidence of MSI, p16 methylation, and hMLH1 and MSH2 expression in the Omani population. In addition, a relatively high frequency of CRC in younger age groups was noted, which is an important observation. The left-sided preponderance of MMR defective tumors was mostly associated with hMLH1, and with possible loss of hMSH2 expression, an observation that differs from studies on other populations. In conclusion, although the overall rate of CRC is unknown in this region, the frequency of MSI in CRC in this region appears to be the same as in Caucasians in the USA.

Autozygosity mapping of Bardet-Biedl syndrome to 12q21.2 and confirmation of FLJ23560 as BBS10.

Bardet-Biedl syndrome (BBS) is a genetically heterogeneous autosomal recessive disorder characterized by variable obesity, pigmentary retinopathy, polydactyly, mental retardation, hypogonadism and renal failure. In order to identify novel BBS loci we undertook autozygosity mapping studies using high-density SNP microarrays in consanguineous kindreds. We mapped a BBS locus to a 10.1 Mb region at 12q15-q21.2 in a large Omani BBS family (peak lod score 8.3 at theta = 0.0 for marker D12S1722) that contained the recently described BBS10 locus. Mutation analysis of candidate genes within the target interval, including the BBS10 gene, revealed a homozygous frameshift mutation in FLJ23560 and mutations were also detected in four smaller consanguineous families with regions of autozygosity at 12q21.2. These findings (a) confirm a previous report that FLJ23560 (BBS10) mutations are a significant cause of BBS, and (b) further demonstrate the utility of high-density SNP array mapping in consanguineous families for the mapping and identification of recessive disease genes.

Collecting genetic information in primary care: evaluating a new family history tool.

BACKGROUND: The family history is a time-honoured method for identifying genetic predisposition. In specialist practice the standard approach is to draw up a family tree based on a genetic pedigree interview, but this is too time-consuming and focused on single gene disorders to be applicable in primary care. OBJECTIVES: To assess the ability of a brief self-administered Family History Questionnaire (FHQ), given to patients when they register with a GP, to identify genetic risk. METHODS: A comparative study. Informants completed an FHQ at registration, and later participated in a genetic pedigree interview. Two clinical geneticists independently scored results obtained with each instrument. Discrepancies were agreed by consensus. The genetic risks identified by the two instruments were compared. RESULTS: 326 new registrants completed the FHQ, and 121 also completed the genetic interview. 24% of FHQs and 36% of genetic interviews resulted in a score 'higher than population risk'. There was 77% agreement in the scores obtained with the two instruments, with a moderate kappa of 0.52. (95% CI 0.40-0.64). There was 90% agreement in the scores for a family history of premature coronary heart disease (Kappa 0.67; 95% CI 0.49 to 0.85). The instruments were equally effective in identifying ethnicity-related risk of common recessive disorders. CONCLUSIONS: The FHQ identified most informants with genetic risks that are appropriately addressed in primary care-those with a family history of premature coronary heart disease, those warranting specialist referral, and those who might appropriately be offered carrier testing. However, it was less effective in identifying those with a possible Mendelian disorder for whom more information was required.

The phenotypic spectrum of baraitser-winter syndrome: a new case and review of literature.

The syndrome of iris coloboma, ptosis, hypertelorism, and mental retardation (Online Mendelian Inheritance in Man -- OMIM # 243310), also known as the Baraitser-Winter syndrome, originally was described in a brother and sister and in an unrelated girl in 1988. Six additional individuals with a similar phenotype have been reported in the world literature. Microphthalmos, microcornea, and brain malformations were added to the phenotypic spectrum of this syndrome in 1995. We report a child who presented with the aforementioned findings. Eye examination revealed bilateral microphthalmos and typical iris, optic nerve, and choroidal colobomas. Magnetic resonance imaging of the brain demonstrated pachygyria and cortical atrophy.

Genetic information and testing in insurance and employment: technical, social and ethical issues.

The present paper examines the professional and scientific views on the social, ethical and legal issues that impact on genetic information and testing in insurance and employment in Europe. For this purpose, many aspects have been considered, such as the concerns of medical geneticists, of the insurers and employers, of the public, as well as the regulatory frameworks and unresolved issues. The method used was primarily the review of the technical, social, economical and ethical aspects of advances in genetics and the concerns of parties who are involved, that is, the insurers, the employers and the public. The existing guidelines and legislation on this topic were also reported. Then, the method was to examine the issues debated by these parties in Europe, as well as by 47 experts from 14 European countries invited to an international workshop organized by the European Society of Human Genetics Public and Professional Policy Committee in Manchester, UK, 25-27 February 2000. The result of this was that the most important issues raised by genetic information and testing in insurance and employment in Europe include a need for clear definitions of terms used in genetics, declaring the grounds on which genetic information is or is not used, and promoting confidence between the public and the insurance industry. There is currently very little use of genetic information in relation to employment, but the situation should be kept under review.

Implications of genetic testing for the insurance industry: the UK example.

This report summarises the controversy of genetic tests and insurance, with a focus on the UK situation during the past decade. UK experience provides insight for future strategies to help people with genetic disadvantages make insurance provision for themselves and their families. Non-disclosure of genetic test results (already carried out for clinical purposes) may not benefit people at risk of genetic disorders or with positive genetic tests. The pressure of geneticists over a decade to prevent disclosure to insurers may have masked opportunities to use insurance to provide help for people with genetic disadvantages. To seize the opportunities now, there must be collaboration, not conflict. Politicians, geneticists, social scientists and all elements of the insurance industry can contribute to wise solutions.

Genetic counselling issues and male infertility.

In the past few years, the major genetic causes of male infertility have been elucidated and many of these can now be treated using intracytoplasmic sperm injection (ICSI). This has raised a number of wider issues in the families of people with this type of infertility. Coupled with the essential need for individual (or family) confidentiality, this type of treatment demands a very careful and sensitive counselling approach. The main requirement is for fertility and genetic teams to collaborate to provide a person-oriented approach to the application of two very complex and intimidating technologies. An apparent difference between established fertility approaches and those of genetic teams relates to individual informed choice. The fertility team must address 'the welfare of the child' as is encapsulated in the Human Fertilisation and Embryology Authority (HFEA) Act of 1990. Since the welfare of the child is a subjective matter, decisions are often made by reproductive medicine ethics committees in conjunction with fertility teams. This aspect requires further development to include the ethos of genetic counselling, which is based more on individual informed choice for couples who have been provided with accurate information about the impact of a condition on a possible future child. The different ethical emphasis is not as great as it might initially appear. Ethics committees are now placing much more emphasis on a couple's autonomy in individual situations and, correspondingly, genetic centres are providing much more information about the possible effects of a couple's decision on the welfare of future children.