MKS1 regulates ciliary INPP5E levels in Joubert syndrome.

BACKGROUND: Joubert syndrome (JS) is a recessive ciliopathy characterised by a distinctive brain malformation 'the molar tooth sign'. Mutations in >27 genes cause JS, and mutations in 12 of these genes also cause Meckel-Gruber syndrome (MKS). The goals of this work are to describe the clinical features of MKS1-related JS and determine whether disease causing MKS1 mutations affect cellular phenotypes such as cilium number, length and protein content as potential mechanisms underlying JS. METHODS: We measured cilium number, length and protein content (ARL13B and INPP5E) by immunofluorescence in fibroblasts from individuals with MKS1-related JS and in a three-dimensional (3D) spheroid rescue assay to test the effects of disease-related MKS1 mutations. RESULTS: We report MKS1 mutations (eight of them previously unreported) in nine individuals with JS. A minority of the individuals with MKS1-related JS have MKS features. In contrast to the truncating mutations associated with MKS, all of the individuals with MKS1-related JS carry ≥ 1 non-truncating mutation. Fibroblasts from individuals with MKS1-related JS make normal or fewer cilia than control fibroblasts, their cilia are more variable in length than controls, and show decreased ciliary ARL13B and INPP5E. Additionally, MKS1 mutant alleles have similar effects in 3D spheroids. CONCLUSIONS: MKS1 functions in the transition zone at the base of the cilium to regulate ciliary INPP5E content, through an ARL13B-dependent mechanism. Mutations in INPP5E also cause JS, so our findings in patient fibroblasts support the notion that loss of INPP5E function, due to either mutation or mislocalisation, is a key mechanism underlying JS, downstream of MKS1 and ARL13B.

Chorionic Villus Sampling, Early Amniocentesis, and Termination of Pregnancy Without Diagnostic Testing: Comparison of Fetal Risk Following Positive Non-invasive Prenatal Testing.

BACKGROUND: With the increased accuracy of non-invasive prenatal testing (NIPT) based on cell-free DNA (cfDNA) techniques, the likelihood of false-positive screening results has been reduced for high-risk populations. Following a positive screening test, a diagnostic procedure to confirm the result is strongly recommended, although some patients have terminated pregnancies because of a positive NIPT alone. Chorionic villus sampling (CVS), the diagnostic procedure of choice in the first trimester, is not available in all locations. Amniocentesis before 15 weeks, referred to as early amniocentesis (EA), is associated with a 1% rate of talipes and an increased rate of early pregnancy loss compared with CVS. Our objective was to compare the level of risk for euploid pregnancies following a positive NIPT based on the invasive procedure chosen. METHOD: Using data from a 2003 meta-analysis, we estimated the rates of adverse pregnancy outcome in euploid pregnancies based on the positive predictive value (PPV) of NIPT and the invasive procedure used-that is, CVS, EA, or termination of pregnancy (TOP). RESULTS: Following NIPT, we found that the rate of adverse fetal outcomes in euploid pregnancies was lower for CVS than for EA at all PPV levels. As the PPV of NIPT increased, the difference in risk between EA and CVS decreased. The risk to euploid pregnancies of TOP was excessive at all PPVs. CONCLUSION: CVS is the recommended diagnostic test in the first trimester because it is safer than EA for the fetus. However, EA is better than no testing when early TOP is planned. Patients should be strongly counselled against TOP without confirmatory testing.

Noninvasive prenatal testing: limitations and unanswered questions.

The clinical use of noninvasive prenatal testing to screen high-risk patients for fetal aneuploidy is becoming increasingly common. Initial studies have demonstrated high sensitivity and specificity, and there is hope that these tests will result in a reduction of invasive diagnostic procedures as well as their associated risks. Guidelines on the use of this testing in clinical practice have been published; however, data on actual test performance in a clinical setting are lacking, and there are no guidelines on quality control and assurance. The different noninvasive prenatal tests employ complex methodologies, which may be challenging for health-care providers to understand and utilize in counseling patients, particularly as the field continues to evolve. How these new tests should be integrated into current screening programs and their effect on health-care costs remain uncertain.

Duplication within the SEPT9 gene associated with a founder effect in North American families with hereditary neuralgic amyotrophy.

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant disorder associated with recurrent episodes of focal neuropathy primarily affecting the brachial plexus. Point mutations in the SEPT9 gene have been previously identified as the molecular basis of HNA in some pedigrees. However in many families, including those from North America demonstrating a genetic founder haplotype, no sequence mutations have been detected. We report an intragenic 38 Kb SEPT9 duplication that is linked to HNA in 12 North American families that share the common founder haplotype. Analysis of the breakpoints showed that the duplication is identical in all pedigrees, and molecular analysis revealed that the duplication includes the 645 bp exon in which previous HNA mutations were found. The SEPT9 transcript variants that span this duplication contain two in-frame repeats of this exon, and immunoblotting demonstrates larger molecular weight SEPT9 protein isoforms. This exon also encodes for a majority of the SEPT9 N-terminal proline rich region suggesting that this region plays a role in the pathogenesis of HNA.

Improving knowledge about prenatal screening options: can group education make a difference?

OBJECTIVE: To determine if the addition of group education regarding maternal serum screening and diagnostic testing for aneuploidy and neural tube defects improves patient knowledge and affects the uptake of testing compared to individual education alone. METHOD: We conducted a prospective study of 443 obstetric patients to assess knowledge of prenatal testing options based on individual provider counseling (n = 331) or provider counseling with supplemental group education (n = 112). We used a chi-square test to compare the number of correct survey answers between the two groups. RESULTS: There was no difference in baseline knowledge. Patients receiving group education showed a statistically significant improvement in knowledge. After initiation of group education, the uptake of maternal serum screening declined while the uptake of amniocentesis remained unchanged. CONCLUSION: Group education in addition to individual counseling to discuss prenatal testing options appears to be effective in improving knowledge compared to individual provider counseling alone. Improved knowledge may affect uptake of prenatal screening tests due to more informed decision making.