IHH enhancer variant within neighboring NHEJ1 intron causes microphthalmia anophthalmia and coloboma

Genomic sequences residing within introns of few genes have been shown to act as enhancers affecting expression of neighboring genes. We studied an autosomal recessive phenotypic continuum of microphthalmia, anophthalmia and ocular coloboma, with no apparent coding-region disease-causing mutation. Homozygosity mapping of several affected Jewish Iranian families, combined with whole genome sequence analysis, identified a 0.5 Mb disease-associated chromosome 2q35 locus (maximal LOD score 6.8) harboring an intronic founder variant in NHEJ1, not predicted to affect NHEJ1. The human NHEJ1 intronic variant lies within a known specifically limb-development enhancer of a neighboring gene, Indian hedgehog (Ihh), known to be involved in eye development in mice and chickens. Through mouse and chicken molecular development studies, we demonstrated that this variant is within an Ihh enhancer that drives gene expression in the developing eye and that the identified variant affects this eye-specific enhancer activity. We thus delineate an Ihh enhancer active in mammalian eye development whose variant causes human microphthalmia, anophthalmia and ocular coloboma. The findings highlight disease causation by an intronic variant affecting the expression of a neighboring gene, delineating molecular pathways of eye development.

Lessons learned from expanded reproductive carrier screening in self-reported Ashkenazi, Sephardi, and Mizrahi Jewish patients

Background

Next‐generation sequencing (NGS)‐based panels have gained traction as a strategy for reproductive carrier screening. Their value for screening Ashkenazi Jewish (AJ) individuals, who have benefited greatly from population‐wide targeted testing, as well as Sephardi/Mizrahi Jewish (SMJ) individuals (an underserved population), has not been fully explored.

Methods

The clinical utilization by 6,805 self‐reported Jewish individuals of an expanded NGS panel, along with several ancillary assays, was assessed retrospectively. Data were extracted for a subset of 96 diseases that, during the panel design phase, were classified as being AJ‐, SMJ‐, or pan‐Jewish/pan‐ethnic‐relevant.

Results

64.6% of individuals were identified as carriers of one or more of these 96 diseases. Over 80% of the reported variants would have been missed by following recommended AJ screening guidelines. 10.7% of variants reported for AJs were in “SMJ‐relevant genes,” and 31.2% reported for SMJs were in “AJ‐relevant genes.” Roughly 2.5% of individuals carried a novel, likely pathogenic variant. One in 16 linked cohort couples was identified as a carrier couple for at least one of these 96 diseases.

Conclusion

For maximal carrier identification, this study supports using expanded NGS panels for individuals of all Jewish backgrounds. This approach can better empower at‐risk couples for reproductive decision making.

Nationwide genetic analysis for molecularly unresolved cystic fibrosis patients in a multiethnic society: implications for preconception carrier screening

Background

Preconception carrier screening for cystic fibrosis (CF) is usually performed using ethnically targeted panels of selected mutations. This has been recently challenged by the use of expanded, ethnically indifferent, pan‐population panels. Israel is characterized by genetically heterogeneous populations carrying a wide range of CFTR mutations. To assess the potential of expanding the current Israeli preconception screening program, we sought the subset of molecularly unresolved CF patients listed in the Israeli CF data registry comprising ~650 patients.

Methods

An Israeli nationwide genotyping of 152 CF cases, representing 176 patients lacking molecular diagnosis, was conducted. Molecular analysis included Sanger sequencing for all exons and splice sites, multiplex ligation probe amplification (MLPA), and next‐generation sequencing of the poly‐T/TG tracts.

Results

We identified 54 different mutations, of which only 16 overlapped the 22 mutations included in the Israeli preconception screening program. A total of 29/54 (53.7%) mutations were already listed as CF causing by the CFTR2 database, and only 4/54 (7.4%) were novel. Molecular diagnosis was reached in 78/152 (51.3%) cases. Prenatal diagnosis of 24/78 (30.8%) cases could have been achieved by including all CFTR2‐causing mutations in the Israeli panel.

Conclusions

Our data reveal an overwhelming hidden abundance of CFTR gene mutations suggesting that expanded preconception carrier screening might achieve higher preconception detection rates.

Characteristics of diabetes after pediatric liver transplant

Studies of DALT in pediatric recipients describe incidence and risk factors, but diagnostic criteria varied. This study reports characteristics and course of pediatric DALT by established diabetes criteria. Retrospective chart review of pediatric LT recipients evaluated for hyperglycemia (1/1/1997-12/30/2009) and matched, non-diabetic controls. DALT: random blood glucose >11.1 mm, ≥ 2 times, with insulin treatment. DALT diagnosed in 8.0% (24/300) included 7/24 (29.2%) with severe hyperglycemia (>27.7 mm), ketoacidosis in 2/24 (8.3%). At diagnosis, age was ≥ 11 yr old in 22/24 (91.7%); body mass was lean (BMIz -0.2 ± 1.5). Mean blood glucose was 24.6 mm with negative diabetes autoantibodies (19/19) and elevated C-peptide (2.3 nm). DALT onset median 5.0 months included 29.1% >12 months. Insulin duration median 4.6 months included 41.7% >6 months. DALT resolved in 83.3% over 4.9 (0.9-9.1) yr. DALT differed from controls by increased preceding rejections, prednisolone dose, tacrolimus level, and triple immunosuppression (all p < 0.01). In conclusion, pediatric DALT occurred in non-obese adolescents with insulin resistance, distinct from diabetes types 1 or 2. DALT was associated with preceding rejection and increased immunosuppression. Blood glucose monitoring, especially during increased immunosuppression following LT, could allow early diagnosis and reduce morbidity.

Prenatal diagnosis of a pulmonary arteriovenous malformation

Pulmonary arteriovenous malformations (PAVMs) are caused by abnormal communications between pulmonary arteries and pulmonary veins. They are most often congenital, and may occur as isolated lesions or part of complex congenital syndromes. We describe a case of PAVM in a 16-week-old fetus. To the best of our knowledge this is the first case to be described in the literature of diagnosis, at such an early gestational age, of PAVM with the shunt found between the main pulmonary artery and pulmonary vein.