Paraspeckles are mammalian subnuclear bodies built on a long noncoding RNA and are enriched in RNA binding proteins with prion-like domains; two of these proteins, RBM14 and FUS, use these domains to hold paraspeckles together.

No abstract

Array-based technologies have led to the identification of many novel microdeletion and microduplication syndromes demonstrating multiple congenital anomalies and intellectual disability (MCA/ID). We have used chromosomal microarray analysis for the evaluation of patients with MCA/ID and/or neonatal hypotonia. Three overlapping de novo microdeletions at 5q31.3 with the shortest region of overlap (SRO) of 370 kb were detected in three unrelated patients. These patients showed similar clinical features including severe neonatal hypotonia, neonatal feeding difficulties, respiratory distress, characteristic facial features, and severe developmental delay. These features are consistent with the 5q31.3 microdeletion syndrome originally proposed by Shimojima et al., providing further evidence that this syndrome is clinically discernible. The 370 kb SRO encompasses only four RefSeq genes including neuregulin 2 (NRG2) and purine-rich element binding protein A (PURA). NRG2 is one of the members of the neuregulin family related to neuronal and glial cell growth and differentiation, thus making NRG2 a good candidate for the observed phenotype. Moreover, PURA is also a good candidate because Pura-deficient mice demonstrate postnatal neurological manifestations.

FOXG1 on chromosome 14 has recently been suggested as a dosage-sensitive gene. Duplication of this gene could cause severe epilepsy and developmental delay, including infantile spasms. Here, we report on a female patient diagnosed with maternal uniparental disomy of chromosome 14 and West syndrome who carried a small supernumerary marker chromosome. A chromosomal analysis revealed mosaicism of 47,XX, + mar[8]/46,XX[18]. Spectral karyotyping multicolor fluorescence in situ hybridization analysis confirmed that the marker chromosome was derived from chromosome 14. A DNA methylation test at MEG3 in 14q32.2 and microsatellite analysis using polymorphic markers on chromosome 14 confirmed that the patient had maternal uniparental disomy 14 as well as a mosaic small marker chromosome of paternal origin containing the proximal long arm of chromosome 14. Microarray-based comparative genomic hybridization analysis conclusively defined the region of the gain of genomic copy numbers at 14q11.2-q12, encompassing FOXG1. The results of the analyses of our patient provide further evidence that not only duplication but also a small increase in the dosage of FOXG1 could cause infantile spasms.

SLC9A6 mutations have been reported in families in whom X-linked mental retardation (XMR) mimics Angelman syndrome (AS). However, the relative importance of SLC9A6 mutations in patients with an AS-like phenotype or XMR has not been fully investigated. Here, the involvement of SLC9A6 mutations in 22 males initially suspected to have AS but found on genetic testing not to have AS (AS-like cohort), and 104 male patients with XMR (XMR cohort), was investigated. A novel SLC9A6 mutation (c.441delG, p.S147fs) was identified in one patient in the AS-like cohort, but no mutation was identified in XMR cohort, suggesting mutations in SLC9A6 are not a major cause of the AS-like phenotype or XMR. The patient with the SLC9A6 mutation showed the typical AS phenotype, further demonstrating the similarity between patients with AS and those with SLC9A6 mutations. To clarify the effect of the SLC9A6 mutation, we performed RT-PCR and Western blot analysis on lymphoblastoid cells from the patient. Expression of the mutated transcript was significantly reduced, but was restored by cycloheximide treatment, indicating the presence of nonsense mediated mRNA decay. Western blot analysis demonstrated absence of the normal NHE6 protein encoded for by SLC9A6. Taken together, these findings indicate a loss-of-function mutation in SLC9A6 caused the phenotype in our patient.