Differential regulation of two FLNA transcripts explains some of the phenotypic heterogeneity in the loss-of-function filaminopathies.

Loss-of-function mutations in the X-linked gene FLNA can lead to abnormal neuronal migration, vascular and cardiac defects, and congenital intestinal pseudo-obstruction (CIPO), the latter characterized by anomalous intestinal smooth muscle layering. Survival in male hemizygotes for such mutations is dependent on retention of residual FLNA function but it is unclear why a subgroup of males with mutations in the 5' end of the gene can present with CIPO alone. Here, we demonstrate evidence for the presence of two FLNA isoforms differing by 28 residues at the N-terminus initiated at ATG+1 and ATG+82 . A male with CIPO (c.18_19del) exclusively expressed FLNA ATG+82 , implicating the longer protein isoform (ATG+1 ) in smooth muscle development. In contrast, mutations leading to reduction of both isoforms are associated with compound phenotypes affecting the brain, heart, and intestine. RNA-seq data revealed three distinct transcription start sites, two of which produce a protein isoform utilizing ATG+1 while the third utilizes ATG+82 . Transcripts sponsoring translational initiation at ATG+1 predominate in intestinal smooth muscle, and are more abundant compared with the level measured in fibroblasts. Together these observations describe a new mechanism of tissue-specific regulation of FLNA that could reflect the differing mechanical requirements of these cell types during development.

Erratum: Hwang Y.T. et al. Molecular Inconsistencies in a Fragile X Male with Early Onset Ataxia. Genes 2016, 7, 68.

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Molecular Inconsistencies in a Fragile X Male with Early Onset Ataxia.

Mosaicism for FMR1 premutation (PM: 55-199 CGG)/full mutation (FM: >200 CGG) alleles or the presence of unmethylated FM (UFM) have been associated with a less severe fragile X syndrome (FXS) phenotype and fragile X associated tremor/ataxia syndrome (FXTAS)-a late onset neurodegenerative disorder. We describe a 38 year old male carrying a 100% methylated FM detected with Southern blot (SB), which is consistent with complete silencing of FMR1 and a diagnosis of fragile X syndrome. However, his formal cognitive scores were not at the most severe end of the FXS phenotype and he displayed tremor and ataxic gait. With the association of UFM with FXTAS, we speculated that his ataxia might be related to an undetected proportion of UFM alleles. Such UFM alleles were confirmed by more sensitive PCR based methylation testing showing FM methylation between 60% and 70% in blood, buccal, and saliva samples and real-time PCR analysis showing incomplete silencing of FMR1. While he did not meet diagnostic criteria for FXTAS based on MRI findings, the underlying cause of his ataxia may be related to UFM alleles not detected by SB, and follow-up clinical and molecular assessment are justified if his symptoms worsen.

Recognizable cerebellar dysplasia associated with mutations in multiple tubulin genes.

Mutations in alpha- and beta-tubulins are increasingly recognized as a major cause of malformations of cortical development (MCD), typically lissencephaly, pachygyria and polymicrogyria; however, sequencing tubulin genes in large cohorts of MCD patients has detected tubulin mutations in only 1-13%. We identified patients with a highly characteristic cerebellar dysplasia but without lissencephaly, pachygyria and polymicrogyria typically associated with tubulin mutations. Remarkably, in seven of nine patients (78%), targeted sequencing revealed mutations in three different tubulin genes (TUBA1A, TUBB2B and TUBB3), occurring de novo or inherited from a mosaic parent. Careful re-review of the cortical phenotype on brain imaging revealed only an irregular pattern of gyri and sulci, for which we propose the term tubulinopathy-related dysgyria. Basal ganglia (100%) and brainstem dysplasia (80%) were common features. On the basis of in silico structural predictions, the mutations affect amino acids in diverse regions of the alpha-/beta-tubulin heterodimer, including the nucleotide binding pocket. Cell-based assays of tubulin dynamics reveal various effects of the mutations on incorporation into microtubules: TUBB3 p.Glu288Lys and p.Pro357Leu do not incorporate into microtubules at all, whereas TUBB2B p.Gly13Ala shows reduced incorporation and TUBA1A p.Arg214His incorporates fully, but at a slower rate than wild-type. The broad range of effects on microtubule incorporation is at odds with the highly stereotypical clinical phenotype, supporting differential roles for the three tubulin genes involved. Identifying this highly characteristic phenotype is important due to the low recurrence risk compared with the other (recessive) cerebellar dysplasias and the apparent lack of non-neurological medical issues.

Diverse phenotypic consequences of mutations affecting the C-terminus of FLNA.

UNLABELLED: Filamin A, the filamentous protein encoded by the X-linked gene FLNA, cross-links cytoskeletal actin into three-dimensional networks, facilitating its role as a signalling scaffold and a mechanosensor of extrinsic shear forces. Central to these functions is the ability of FLNA to form V-shaped homodimers through its C-terminal located filamin repeat 24. Additionally, many proteins that interact with FLNA have a binding site that includes the C-terminus of the protein. Here, a cohort of patients with mutations affecting this region of the protein is studied, with particular emphasis on the phenotype of male hemizygotes. Seven unrelated families are reported, with five exhibiting a typical female presentation of periventricular heterotopia (PH), a neuronal migration disorder typically caused by loss-of-function mutations in FLNA. One male presents with widespread PH consistent with previous male phenotypes attributable to hypomorphic mutations in FLNA. In stark contrast, two brothers are described with a mild PH presentation, due to a missense mutation (p.Gly2593Glu) inserting a large negatively charged amino acid into the hydrophobic dimerisation interface of FLNA. Co-immunoprecipitation, in vitro cross-linking studies and gel filtration chromatography all demonstrated that homodimerisation of isolated FLNA repeat 24 is abolished by this p.Gly2593Glu substitution but that extended FLNA(Gly2593Glu) repeat 16-24 constructs exhibit dimerisation. These observations imply that other interactions apart from those mediated by the canonical repeat 24 dimerisation interface contribute to FLNA homodimerisation and that mutations affecting this region of the protein can have broad phenotypic effects. KEY MESSAGES: • Mutations in the X-linked gene FLNA cause a spectrum of syndromes. • Genotype-phenotype correlations are emerging but still remain unclear. • C-term mutations can confer male lethality, survival or connective tissue defects. • Mutations leading to the latter affect filamin dimerisation. • This deficit is compensated for by remotely acting domains elsewhere in FLNA.

Carbimazole/methimazole embryopathy in siblings: a possible genetic susceptibility.

BACKGROUND: The teratogenic effects of antenatal exposure of antithyroid drugs, carbimazole and methimazole have been well reported in the literature. These comprise of typical facial features and a wide variety of malformations such as choanal atresia, tracheo-esophageal anomalies, congenital heart disease and ectodermal defects. However, the longitudinal studies have failed to establish the consistent teratogenicity of these drugs. CASES: we report here two siblings with physical features consistent with carbimazole/methimazole embryopathy. We also describe previously unreported minor dental anomalies in these siblings with antenatal exposure of carbimazole. CONCLUSION: Generally, only a small proportion of prenatally exposed children have the typical manifestations, and the presence in siblings supports a possible hereditary susceptibility to carbimazole/ methimazole embryopathy. This highlights the importance of recognizing this diagnosis before a subsequent pregnancy.

Missense mutations in ITPR1 cause autosomal dominant congenital nonprogressive spinocerebellar ataxia.

BACKGROUND: Congenital nonprogressive spinocerebellar ataxia is characterized by early gross motor delay, hypotonia, gait ataxia, mild dysarthria and dysmetria. The clinical presentation remains fairly stable and may be associated with cerebellar atrophy. To date, only a few families with autosomal dominant congenital nonprogressive spinocerebellar ataxia have been reported. Linkage to 3pter was demonstrated in one large Australian family and this locus was designated spinocerebellar ataxia type 29. The objective of this study is to describe an unreported Canadian family with autosomal dominant congenital nonprogressive spinocerebellar ataxia and to identify the underlying genetic causes in this family and the original Australian family. METHODS AND RESULTS: Exome sequencing was performed for the Australian family, resulting in the identification of a heterozygous mutation in the ITPR1 gene. For the Canadian family, genotyping with microsatellite markers and Sanger sequencing of ITPR1 gene were performed; a heterozygous missense mutation in ITPR1 was identified. CONCLUSIONS: ITPR1 encodes inositol 1,4,5-trisphosphate receptor, type 1, a ligand-gated ion channel that mediates calcium release from the endoplasmic reticulum. Deletions of ITPR1 are known to cause spinocerebellar ataxia type 15, a distinct and very slowly progressive form of cerebellar ataxia with onset in adulthood. Our study demonstrates for the first time that, in addition to spinocerebellar ataxia type 15, alteration of ITPR1 function can cause a distinct congenital nonprogressive ataxia; highlighting important clinical heterogeneity associated with the ITPR1 gene and a significant role of the ITPR1-related pathway in the development and maintenance of the normal functions of the cerebellum.

Maternal factor V Leiden and adverse pregnancy outcome: deciding whether or not to test.

This narrative review examines the translation from statistical association to change in clinical practice with respect to factor V Leiden and adverse pregnancy outcome. A collation of published meta-analyses illustrates a clear trend towards a greater association with factor V Leiden (fVL) as the severity of adverse pregnancy outcomes increases, and highlights that different study populations are relevant to different clinical scenarios. The yield of fVL testing in women with previous adverse pregnancy outcomes is up to six times higher than in the general population. Calculated post-test probabilities illustrate that the combined effect of fVL and poor pregnancy history places these women at a high-risk of recurrent events. The results to date of low molecular weight heparin (LMWH) treatment trials cannot be extrapolated to all women with thrombophilia; however, the results provide a rationale for randomized prophylactic anticoagulant treatment trials in thrombophilic women with severe adverse pregnancy outcomes. While we await the results of well-designed, adequately powered treatment trials, we propose that post-test probabilities, in addition to the preliminary treatment data in high-risk women, justify consideration of screening for fVL in women with a strong past history of poor pregnancy outcome.

Frameshift mutation hotspot identified in Smith-Magenis syndrome: case report and review of literature.

Smith-Magenis syndrome (SMS) is a complex syndrome involving intellectual disabilities, sleep disturbance, behavioural problems, and a variety of craniofacial, skeletal, and visceral anomalies. While the majority of SMS cases harbor an ~3.5 Mb common deletion on 17p11.2 that encompasses the retinoic acid induced-1 (RAI1) gene, some patients carry small intragenic deletions or point mutations in RAI1. We present data on two cases of Smith-Magenis syndrome with mutation of RAI1. Both cases are phenotypically consistent with SMS and RAI1 mutation but also have other anomalies not previously reported in SMS, including spontaneous pneumothoraces. These cases also illustrate variability in the SMS phenotype not previously shown for RAI1 mutation cases, including hearing loss, absence of self-abusive behaviours, and mild global delays. Sequencing of RAI1 revealed mutation of the same heptameric C-tract (CCCCCCC) in exon 3 in both cases (c.3103delC one case and and c.3103insC in the other), resulting in frameshift mutations. Of the seven reported frameshift mutations occurring in poly C-tracts in RAI1, four cases (~57%) occur at this heptameric C-tract. Collectively, these results indicate that this heptameric C-tract is a preferential hotspot for single nucleotide insertion/deletions (SNindels) and therefore, should be considered a primary target for analysis in patients suspected for mutations in RAI1. We expect that as more patients are sequenced for mutations in RAI1, the incidence of frameshift mutations in this hotspot will become more evident.

Lessons from the skin--cutaneous features of familial cancer.

As the molecular basis of disease continues to be elucidated, familial cancer syndromes, which consist of a range of neoplastic and non-neoplastic features, are emerging. The usual pathway of referral to a genetics clinic or familial cancer centre is via an oncologist, when high-risk features that suggest a possible hereditary basis for the presenting cancer are recognised. Traditionally, these high-risk features include more than two family members with similar cancers over two or more generations, a young age of onset, and more than one synchronous or metachronous tumour. These features are effective in ascertaining a substantial proportion of families with hereditary breast and ovarian cancer due to a BRCA mutation, or the more common bowel-cancer predisposition syndromes, such as hereditary non-polyposis colon cancer and familial adenomatous polyposis. However, there are a range of familial cancer syndromes that are not easily detected and that can remain undiagnosed when history and examination are not extended to include non-malignant features. The identification of cutaneous signs associated with rare familial-cancer syndromes provides individuals and their families with the opportunity to undertake early surveillance for malignant and non-malignant complications that might in time be shown to improve outcomes.

Atypical Angelman syndrome with macrocephaly due to a familial imprinting center deletion.

Two elderly brothers with severe intellectual disability were diagnosed with Angelman syndrome after a once-removed, 15-year-old cousin was found to have the syndrome due to a deletion of the imprinting center. For many years it was believed the brothers, who both have macrocephaly, were affected by nonsyndromic X-linked mental retardation. This was because, apart from absent speech and intellectual disability, the phenotype of the two men was not characteristic of Angelman syndrome. Conversely, the cousin, in addition to severe intellectual disability, language impairment, and ataxic gait, has microcephaly. None of the three have seizures, and so in the presence of the brothers' macrocephaly, Angelman syndrome was not considered until a diagnosis was made in the younger distant cousin. We report on a familial imprinting center deletion and the importance of considering the mild and atypical Angelman syndrome phenotypes within the differential diagnosis of intellectual handicap, particularly in clarifying the genetic risk to other family members.

A randomized controlled trial of a decision aid for women considering genetic testing for breast and ovarian cancer risk.

PURPOSE: To measure the effectiveness of a tailored decision aid (DA) designed to help women make informed decisions about genetic testing for breast/ovarian cancer risk. METHODS: A total of 145 women were randomized to receive the DA or a control pamphlet at the end of their first genetic counseling consultation. Of these, 120 (82.8%) completed two questionnaires, 1 week and 6 months post-consultation. RESULTS: While the DA had no effect on informed choice, post-decisional regret or actual genetic testing decision, the trial showed that women who received the DA had higher knowledge levels and felt more informed about genetic testing than women who received the control pamphlet (chi(2)(2) = 6.82; P = 0.033; chi(2)(1) = 4.86; P = 0.028 respectively). The DA also helped women who did not have blood drawn at their first consultation to clarify their values with regards to genetic testing (chi(2)(1) = 5.27; P = 0.022). Women who received the DA were less likely to share the information with other family members than women in the control condition (chi(2)(1) = 8.78; P = 0.003). CONCLUSIONS: Decision aids are an effective decision-support strategy for women considering genetic testing for breast/ovarian cancer risk, and are most effective before the patient has made a decision, which is generally at the point of having blood drawn.

Screening behavior in women at increased familial risk for breast cancer.

This multicenter study examined the adherence of high-risk women to screening recommendations for breast and ovarian cancer following consultation at a familial cancer clinic (FCC). Self-report questionnaires assessing recall of screening advice, tests undertaken, risk perception, anxiety (Impact of Events Scale) and demographics were mailed to 396 consecutive eligible women who had attended one of six FCCs a median of 3.6 years prior. Family history, genetic test results and screening recommendations were abstracted from medical records. 182/266 (68.4%) women responded with 130 lost to follow-up. The proportions of women undertaking at least the recommended frequency of screening tests were: breast self examination (BSE) 50.4%, clinical breast examination (CBE) 66.0%, mammography 82.2%, transvaginal ultrasound (TVUS) 70.0%, CA125 84.0%. Factors associated with adherence to screening were: higher anxiety for BSE and CBE, being BRCA1/2 positive for CBE, older age, method of arrangement and having at least one affected first degree relative for mammography. Factors significantly associated with over-adherence were higher scores for anxiety for BSE and CBE and younger age (< 40 years) for TVUS. Between 41.3% (BSE) and 57.6% (CBE) of women incorrectly recalled their screening recommendations. A substantial minority of high-risk women do not adhere to screening advice. Strategies to improve the accuracy of recall of recommendations and the uptake of recommended screening are required.

Risk-reducing surgery in women with familial susceptibility for breast and/or ovarian cancer.

This multicentre study examined uptake of bilateral risk-reducing mastectomy (BRRM) and bilateral risk-reducing oophorectomy (BRRO) in women at increased risk for breast and/or ovarian cancer who had attended a familial cancer clinic (FCC) between January 1999 and June 2000. Eligible women (N=396), were mailed a questionnaire assessing: BRRM and BRRO details; risk perception; and anxiety. Family history, genetic testing and risk assessment were abstracted from medical records. Surgery was cross-tabulated with demographics, risk perception and anxiety with either Fisher's exact test or the exact form of the Mantel-Haenszel test (for ordinal factors) used to investigate for associations. Ordinal logistic regression was used with continuous-scale covariates. In total, 130 women were lost to follow-up leaving 266; of these 182 (68.4%) responded. Mean follow-up time was 3.73 years. The BRRM rate was 4.4%; with no difference found between moderate and high-risk groups. BRRM was associated with increasing numbers of affected relatives (P=0.025). BRRO was undertaken by 17.3%, more commonly in women older than 40 years of age (P=0.023) and with a BRCA1/2 mutation (P=0.017). Women who underwent BRRM (P=0.052) or BRRO (P<0.001) had a lower post-procedure risk perception than those who did not. During the timeframe of this study, risk-reducing surgery was undertaken by a small percentage of Australian women at increased risk for breast and/or ovarian cancer who attended FCCs. Family cancer history and mutation status were associated with uptake.

The association between adverse pregnancy outcomes and maternal factor V Leiden genotype: a meta-analysis.

The conclusions of studies to date which evaluate a possible association between factor V Leiden and adverse pregnancy outcome have been conflicting. This study was undertaken to further investigate this association. Our objective was to evaluate the association between adverse pregnancy outcomes and maternal factor V Leiden genotype by meta-analysis. Inclusion criteria were: (a) cohort or case control design; (b) outcomes clearly defined as one of the following: first or second/ third trimester miscarriage or intrauterine death, preeclampsia, fetal growth retardation, or placental abruption; (c) both the case and control mothers tested for the factor V Leiden mutation; (d) sufficient data for calculation of an odds ratio. Both fixed and random effect models were used to pool results and heterogeneity and publication bias were checked. For first trimester fetal loss, the pooled odds ratio was heterogeneous (p=0.06) and no dose-response curve could be found. For second/third trimester fetal loss, there was a consistent and graded increase in risk: the odds ratio was 2.4 (95% CI 1.1-5.2) for isolated (non-recurrent) third trimester fetal loss, rising to 10.7 (95% CI 4.0-28.5) for those with 2 or more second/third trimester fetal losses. Factor V Leiden is associated with a 2.9 fold (95% CI 2.0-4.3) increased risk of severe preeclampsia, and a 4.8 fold (95% CI 2.4-9.4) increased risk of fetal growth retardation. These results support factor V Leiden testing for women with recurrent fetal loss in the second/third trimester. Women with only 1 event may also warrant testing if the fetal loss occurred in the third trimester. Conversely, in those women known to have the factor V Leiden mutation, monitoring for adverse pregnancy outcomes is warranted; whether this means increased vigilance or anti-coagulant prophylaxis is still contentious.