Establishing intellectual disability as the key feature of patients with biallelic RNPC3 variants.

Some mammalian genes contain both major and minor introns, the splicing of which require distinctive major and minor spliceosomes, respectively; these genes are referred to as minor intron containing-genes. RNPC3 (RNA-binding domain-containing protein 3) is one of the proteins that are unique to the minor spliceosome U11/U12 di-snRNP. Only two families with biallelic pathogenic variants in the RNPC3 gene encoding the protein have been reported so far, and the affected members in both families had proportional short stature. While the affected members of the originally identified family did not have intellectual disability, the patients from the other family exhibited intellectual disability. Here, we report on a patient with severe primordial microcephalic dwarfism and intellectual disability who carried compound heterozygous variants in RNPC3 (NM_017619.3): c.261dup, p.Leu88Thrfs*11 and c.1228T>G, p.Phe410Val. The single nucleotide substitution c.1228T>G had a very high predictive score for pathogenicity: the p.Phe410 residue is highly conserved down to fish. Based on ACMG (American College of Medical Genetics and Genomics) guideline, this non-synonymous variant was scored as likely pathogenic. This documentation of yet another patient with biallelic RNPC3 variants exhibiting intellectual disability lends further support to the notion that intellectual disability is a key feature of the spectrum of RNPC3-related disorders.

Low risk of treatment resistance in Down syndrome with Kawasaki disease.

BACKGROUND: A Japanese nationwide survey has reported that Down syndrome (DS) is a less-frequently occurring comorbidity in Kawasaki disease (KD). Although altered immune responses are frequently observed in DS, no studies have focused on the treatment response and risk for coronary artery abnormalities (CAA) in DS patients with KD. The aim of this study was therefore to evaluate the clinical manifestations, treatment response and prevalence of CAA in DS with KD. METHODS: We retrospectively reviewed the medical records of DS patients with KD from 2005 through 2012. The survey questionnaires were sent to facilities nationwide, and clinical data regarding KD in DS were collected. A control group consisted of non-DS patients with KD who were managed at Toho University. RESULTS: Of the 94 233 children diagnosed with acute KD from 2005 to 2012, 16 children with acute KD also had DS (0.017%). The DS-KD patients were significantly older than the non-DS patients (median, 8 years vs 1 year, P < 0.05, respectively). Half of the DS patients had incomplete KD. Although 50% of the DS children were at high risk of immunoglobulin resistance, all children responded to initial treatment and none had CAA. CONCLUSIONS: All DS-KD patients responded to initial i.v. immunoglobulin (IVIG) or aspirin despite having a high risk of IVIG resistance, and none of the DS patients had CAA. This suggests that the risk of treatment resistance and development of CAA may be not higher in DS patients with acute KD.

Incidence of febrile seizure in patients with Down syndrome.

BACKGROUND: It is unclear whether the incidence of febrile seizure (FS) in children with Down syndrome (DS) is higher or lower than in the general population. In this study, we investigated the incidence of FS in DS patients using mailed questionnaires. METHODS: The questionnaires were distributed to parents or caregivers of DS patients attending Osaka Medical College Hospital and six other facilities. The questionnaires were returned by mail from February 2012 to September 2013 from 323 families of DS patients (176 male, 147 female; age range, 3 months-47 years; median age, 5.0 years). To assess the incidence of FS in DS, we performed the following two analyses: (i) we calculated the incidence of FS among DS patients between the ages of 4 and 20 years (n = 199; 113 male, 86 female), and (ii) we extracted families with both DS and healthy siblings between the ages of 4 and 20 years (n = 150; 77 male, 73 female) and compared the incidence of FS in these sibling groups. RESULTS: Five DS patients had a past history of FS. The incidence of FS in DS was 2.5%. The incidence of FS was significantly lower in DS patients compared with healthy siblings (P < 0.003; OR, 0.14). CONCLUSION: The incidence of FS is lower in DS patients than in the general population.

De novo mutations in the BMPR2 gene in patients with heritable pulmonary arterial hypertension.

A substantial proportion of patients with pulmonary arterial hypertension (PAH) have mutations in the Bone Morphogenetic Protein Receptor type-2 (BMPR2) gene. PAH due to BMPR2 mutations is inherited as an autosomal dominant trait with several unique features, including a wide variety of mutations, reduced penetrance, a skewed gender ratio, variable expressivity and genetic anticipation. To address the genetic background of these unique features of BMPR2 mutation, we conducted a systematic analysis of 15 PAH families with BMPR2 mutation. The exonic protein coding sequence of BMPR2 was amplified by polymerase chain reaction and the products were sequenced directly to detect point mutations in BMPR2. Parental identification was carried out to confirm the parental relationship using multiplex 15 loci analysis. Combining mutation detection in family members with parental identification, we described three cases of de novo mutation in the BMPR2 gene by different modes in a PAH family. These de novo mutations may account for the wide variety of mutations in BMPR2. Taken together with the juvenile onset of the disease, there is possibly some balance of de novo mutations and untransmittable mutations which keeps the frequency of PAH low in the general population.

Presymptomatic genetic analysis during pregnancy for vascular type Ehlers-Danlos syndrome.

The vascular type of Ehlers-Danlos syndrome (EDS), EDS type IV (Online Mendelian Inheritance in Man [MIM] #130050) is characterized by thin, translucent skin, easy bruising, and arterial, intestinal, and/or uterine fragility during pregnancy, which may lead to sudden death. It is an autosomal dominant inherited disorder caused by type III procollagen gene (COL3A1: MIM #120180) mutations. Approximately 50% of the COL3A1 mutations are inherited from an affected parent, and 50% are de novo mutations. Each child of an affected individual has a 50% chance of inheriting the mutation and developing the disorder. Pregnant women with vascular EDS are at an increased risk of uterine and arterial rupture during the peripartum period, with high maternal morbidity and mortality rates. We report the first case of an asymptomatic 35-year-old woman at a risk of complications of vascular EDS who underwent presymptomatic evaluation during pregnancy. The sequencing results of both her brother and mother had a one-base-pair deletion, resulting in Glutamate at position 730 changing to Lysine and causing a frame shift and premature termination codon at 61 amino acids from the mutation position (p. Glu730Lysfs*61) on exon 32 of COL3A1. This deletion caused frameshift, leading to a premature termination codon (TAG) at 181 nucleotides downstream in exon 35, which could not be detected by previous total RNA (ribonucleic acid) method. Thus, she was at risk of complications of vascular EDS, and diagnostic testing was employed at 8 weeks of pregnancy to minimize the risk of developing vascular EDS-related complications. The negative presymptomatic diagnostic result allowed the patient to choose normal delivery at term. Vascular EDS is a serious disorder, with high mortality, especially in high-risk women with vascular EDS during pregnancy. The presymptomatic genetic testing of vascular EDS during pregnancy for a high-risk family can help with the early establishment of preventive measures.

Alu-mediated nonallelic homologous and nonhomologous recombination in the BMPR2 gene in heritable pulmonary arterial hypertension.

PURPOSE: The purpose of this study was to undertake thorough genetic analysis of the bone morphogenetic protein type 2 receptor (BMPR2) gene in patients with pulmonary arterial hypertension. METHODS: We conducted a systematic analysis for larger gene rearrangements together with conventional mutation analysis in 152 pulmonary arterial hypertension patients including 43 patients diagnosed as having idiopathic pulmonary arterial hypertension and 10 diagnosed as having familial pulmonary arterial hypertension. RESULTS: Analysis of the BMPR2 gene revealed each of the four kinds of nonsense and frameshift mutations, one missense mutation, one splice-site mutation, and two types of exonic deletion. For cases in which exons 1-3 were deleted, the 5' and 3' break points were located in the AluY repeat sequences in the 5' side of the adjacent NOP58 gene and in the AluY repeat sequences in intron 3, suggesting an AluY-mediated nonallelic homologous recombination as the mechanism responsible for the deletion. For the case in which exon 10 was deleted, nonhomologous recombination took place between the AluSx site in intron 9 and a unique sequence in intron 10. CONCLUSION: Exonic deletions of BMPR2 account for at least part of BMPR2 mutations associated with heritable pulmonary arterial hypertension in Japan, as previously reported in other populations. One of our cases was mediated via Alu-mediated nonallelic homologous recombination and another was mediated via nonhomologous recombination.

Clinical application of array-based comparative genomic hybridization by two-stage screening for 536 patients with mental retardation and multiple congenital anomalies.

Recent advances in the analysis of patients with congenital abnormalities using array-based comparative genome hybridization (aCGH) have uncovered two types of genomic copy-number variants (CNVs); pathogenic CNVs (pCNVs) relevant to congenital disorders and benign CNVs observed also in healthy populations, complicating the screening of disease-associated alterations by aCGH. To apply the aCGH technique to the diagnosis as well as investigation of multiple congenital anomalies and mental retardation (MCA/MR), we constructed a consortium with 23 medical institutes and hospitals in Japan, and recruited 536 patients with clinically uncharacterized MCA/MR, whose karyotypes were normal according to conventional cytogenetics, for two-stage screening using two types of bacterial artificial chromosome-based microarray. The first screening using a targeted array detected pCNV in 54 of 536 cases (10.1%), whereas the second screening of the 349 cases negative in the first screening using a genome-wide high-density array at intervals of approximately 0.7 Mb detected pCNVs in 48 cases (13.8%), including pCNVs relevant to recently established microdeletion or microduplication syndromes, CNVs containing pathogenic genes and recurrent CNVs containing the same region among different patients. The results show the efficient application of aCGH in the clinical setting.

Fortuitous detection of a submicroscopic deletion at 1q25 in a girl with Cornelia-de Lange syndrome carrying t(5;13)(p13.1;q12.1) by array-based comparative genomic hybridization.

We report on a 2-year-old Japanese girl with Cornelia-de Lange syndrome (CdLS) who had mental and growth retardation, together with characteristic facial anomalies and mild extremity malformations. She had a balanced chromosomal translocation, 46,XX,t(5;13)(p13.1;q12.1) de novo. Surprisingly, this was the same translocation that had provided a clue to the identification of a major causative gene for CdLS, NIPBL [Krantz et al., 2004; Tonkin et al., 2004]. Using fluorescence in situ hybridization (FISH), the breakpoint was confirmed to lie within NIPBL at 5p13.1. Furthermore, array-based comparative genomic hybridization (array-CGH) demonstrated a cryptic 1-Mb deletion harboring six known genes at 1q25-q31.1. A FISH analysis of her parents confirmed that the deletion was de novo. Although patients with interstitial deletions at 1q are rare, some of their features were similar to those observed in our patient, indicating that her clinical manifestations are likely to be affected by not only the disruption of NIPBL but also the concomitant microdeletion at 1q25-q31.1. The present case suggests that array-CGH can uncover cryptic genomic aberrations affecting atypical phenotypes even in well-known congenital disorders.