Bi-allelic variants in INTS11 are associated with a complex neurological disorder.

The Integrator complex is a multi-subunit protein complex that regulates the processing of nascent RNAs transcribed by RNA polymerase II (RNAPII), including small nuclear RNAs, enhancer RNAs, telomeric RNAs, viral RNAs, and protein-coding mRNAs. Integrator subunit 11 (INTS11) is the catalytic subunit that cleaves nascent RNAs, but, to date, mutations in this subunit have not been linked to human disease. Here, we describe 15 individuals from 10 unrelated families with bi-allelic variants in INTS11 who present with global developmental and language delay, intellectual disability, impaired motor development, and brain atrophy. Consistent with human observations, we find that the fly ortholog of INTS11, dIntS11, is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. Using Drosophila as a model, we investigated the effect of seven variants. We found that two (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants, indicating that they are strong loss-of-function variants. Furthermore, we found that five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met, and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. Altogether, our results provide compelling evidence that integrity of the Integrator RNA endonuclease is critical for brain development.

Constitutional Mismatch Repair Deficiency in Israel: High Proportion of Founder Mutations in MMR Genes and Consanguinity.

BACKGROUND: Heterozygous germline mutations in any of the mismatch repair (MMR) genes, MLH1, MSH2, MSH6, and PMS2, cause Lynch syndrome (LS), an autosomal dominant cancer predisposition syndrome conferring a high risk of colorectal, endometrial, and other cancers in adulthood. Offspring of couples where both spouses have LS have a 1:4 risk of inheriting biallelic MMR gene mutations. These cause constitutional MMR deficiency (CMMRD) syndrome, a severe recessively inherited cancer syndrome with a broad tumor spectrum including mainly hematological malignancies, brain tumors, and colon cancer in childhood and adolescence. Many CMMRD children also present with café au lait spots and axillary freckling mimicking neurofibromatosis type 1. PROCEDURE: We describe our experience in seven CMMRD families demonstrating the role and importance of founder mutations and consanguinity on its prevalence. Clinical presentations included brain tumors, colon cancer, lymphoma, and small bowel cancer. RESULTS: In children from two nonconsanguineous Ashkenazi Jewish (AJ) families, the common Ashkenazi founder mutations were detected; these were homozygous in one family and compound heterozygous in the other. In four consanguineous families of various ancestries, different homozygous mutations were identified. In a nonconsanguineous Caucasus/AJ family, lack of PMS2 was demonstrated in tumor and normal tissues; however, mutations were not identified. CONCLUSIONS: CMMRD is rare, but, especially in areas where founder mutations for LS and consanguinity are common, pediatricians should be aware of it since they are the first to encounter these children. Early diagnosis will enable tailored cancer surveillance in the entire family and a discussion regarding prenatal genetic diagnosis.

Homozygous MED25 mutation implicated in eye-intellectual disability syndrome.

Genetic syndromes involving both brain and eye abnormalities are numerous and include syndromes such as Warburg micro syndrome, Kaufman oculocerebrofacial syndrome, Cerebro-oculo-facio-skeletal syndrome, Kahrizi syndrome and others. Using exome sequencing, we have been able to identify homozygous mutation p.(Tyr39Cys) in MED25 as the cause of a syndrome characterized by eye, brain, cardiac and palatal abnormalities as well as growth retardation, microcephaly and severe intellectual disability in seven patients from four unrelated families, all originating from the same village. The protein encoded by MED25 belongs to Mediator complex or MED complex, which is an evolutionary conserved multi-subunit RNA polymerase II transcriptional regulator complex. The MED25 point mutation is located in the von Willebrand factor type A (MED25 VWA) domain which is responsible for MED25 recruitment into the Mediator complex; co-immunoprecipitation experiment demonstrated that this mutation dramatically impairs MED25 interaction with the Mediator complex in mammalian cells.

Genetic carrier screening for spinal muscular atrophy and spinal muscular atrophy with respiratory distress 1 in an isolated population in Israel.

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by progressive muscle weakness. It is caused by a mutation in the survival motor neuron gene 1 (SMN1) gene. SMA with respiratory distress 1 (SMARD1), an uncommon variant of infantile SMA also inherited in an autosomal recessive manner, is caused by mutations in the immunoglobulin mu-binding protein 2 (IGHMBP2) gene. We carried out genetic carrier screening among the residents of an isolated Israeli Arab village with a high frequency of SMA in order to identify carriers of SMA type I and SMARD1. During 2006, 168 women were tested for SMA, of whom 13.1% were found to be carriers. Of 111 women tested for SMARD1, 9.9% were found to be carriers. Prenatal diagnosis was performed in one couple where both spouses were carriers of SMARD1; the fetus was found to be affected, and the pregnancy was terminated. To the best of our knowledge, this is the first example of the establishment of a large-scale carrier-screening program for SMA and SMARD1 in an isolated population. SMA has a carrier frequency of 1:33-1:60 in most populations and should be considered for inclusion in a population-based genetic-screening program.

Genetic screening for autosomal recessive nonsyndromic mental retardation in an isolated population in Israel.

Nonsyndromic mental retardation (NSMR) is the diagnosis of exclusion in mentally retarded individuals without additional abnormalities. We have recently identified a protein-truncating mutation, G408fsX437, in the gene CC2D1A on chromosome 19p13.12 in nine consanguineous Israeli Arab families with severe autosomal recessive NSMR, and have developed a comprehensive prevention program among the at-risk population in the village. The subjects tested were healthy women who were invited to undergo the genetic screening test as a part of their routine pregnancy monitoring. One hundred and seventeen subjects reported a family history positive for mental retardation. We tested 524 pregnant or preconceptional women and found 47 carriers (approximately 1/11), whose spouses were then recommended to undergo testing. We identified eight carrier couples, who were given genetic counseling and offered prenatal diagnosis. Of all the marriages, 28.6% were consanguineous; 16.5% of the total were between first cousins. The high prevalence of the mutation can be explained both by the founder effect owing to the generally high consanguinity rate among the inhabitants of the village, and also because two families with excessive numbers of mentally retarded offspring were unacceptable as marriage partners by the rest of the families. This is the first example of the establishment of a large-scale genetic screening program for autosomal recessive NSMR, which was made possible owing to the high frequency of the specific causative mutation in this isolated population.

Amniotic trisomy 11 mosaicism--is it a benign finding?

OBJECTIVES: A case of prenatally diagnosed trisomy 11 mosaicism with a normal outcome is reported and the medical literature on prenatal detection of this finding is reviewed. METHODS: Proportion of cells with trisomy 11 was evaluated in amniocytes, fetal blood lymphocytes, newborn fibroblasts and urinary epithelial cells. Karyotype studies and fluorescence in situ hybridization analysis using the 11q13LS1 CCND1 probe were performed. RESULTS: Trisomy 11 level III mosaicism of 26% was detected in amniotic fluid cells. Periumbilical blood sampling showed a normal fetal karyotype. No fetal structural abnormalities were noted on ultrasound scan. The infant was spontaneously delivered and had normal physical findings at birth. No evidence of trisomic cells was found on extensive postnatal evaluation, implying an extraembryonic origin. Molecular analysis excluded uniparental disomy of chromosome 11. At 1 year of age, the baby is developing normally. CONCLUSIONS: Only three reports on trisomy 11 mosaicism identified at amniocentesis have been published previously, all with a normal outcome. Additional cases of prenatally diagnosed mosaicism for trisomy 11 are necessary to assess more accurately the clinical significance of this finding.

Mutated nup62 causes autosomal recessive infantile bilateral striatal necrosis.

OBJECTIVE: The objective of this study was to identify the gene causing autosomal recessive infantile bilateral striatal necrosis. METHODS: We have mapped the disease gene in the candidate region to approximately 230kb on 19q13.33 in 8 interrelated families including a total of 12 patients and 39 unaffected individuals. RESULTS: Sequencing of the nup62 gene showed a missense mutation causing a change from glutamine to proline (Q391P) in all the patients, producing a substitution from a polar, hydrophilic residue to a nonpolar, neutral residue. All the other 12 candidate genes were sequenced, and no pathogenic sequence changes were found. Comparisons of p62 protein sequences from diverse species indicate that glutamine at position 391 is highly conserved. Five prenatal diagnoses were performed in three at-risk families. INTERPRETATION: This is the second example of a nuclear pore complex protein causing mendelian disease in humans (the first one is triple A syndrome). Our findings suggest that p62 has a cell type-specific role and is important in the degeneration of the basal ganglia in humans.