Novel sequence variants in the TMC1 gene in Pakistani families with autosomal recessive hearing impairment

Though many hearing impairment genes have been identified, only a few of these genes have been screened in population studies. For this study, 168 Pakistani families with autosomal recessive hearing impairment not due to mutations in the GJB2 (Cx26) gene underwent a genome scan. Two-point and multipoint parametric linkage analyses were carried out. Twelve families had two-point or multipoint LOD scores of 1.4 or greater within the transmembrane cochlear expressed gene 1 (TMC1) region and were subjected to further screening with direct DNA sequencing. Five novel putatively functional non-synonymous sequence variants, c.830A>G (p.Y277C), c.1114G>A (p.V372M), c.1334G>A (p.R445H), c.2004T>G (p.S668R), and c.2035G>A (p.E679K), were found to segregate within seven families, but were not observed in 234 Pakistani control chromosomes. The variants c.830A>G (p.Y277C), c.1114G>A (p.V372M), and c.1334G>A (p.R445H) occurred at highly conserved regions and were predicted to lie within hydrophobic transmembrane domains, while non-synonymous variants c.2004T>G (p.S668R) and c.2035G>A (p.E679K) occurred in extracellular regions that were not highly conserved. There is evidence that the c.2004T>G (p.S668R) variant may have occurred at a phosphorylation site. One family has the known splice site mutation c.536 -8T>A. The prevalence of non-syndromic hearing impairment due to TMC1 in this Pakistani population is 4.4% (95%CI: 1.9, 8.6%). The TMC1 protein might have an important function in K(+) channels of inner hair cells, which would be consistent with the hypothetical structure of protein domains in which sequence variants were identified.     

Hyperoxia-induced DNA damage causes decreased DNA methylation in human lung epithelial-like A549 cells

The effect of hyperoxia on levels of DNA damage and global DNA methylation was examined in lung epithelial-like A549 cells. DNA damage was assessed by the single-cell gel electrophoresis (comet assay) and DNA methylation status by the cytosine extension assays. Cells exposed to ionizing radiation (0, 1, 2, 4, or 8 Gy) showed increasing rates of percentage of DNA in the tail and tail length with increasing radiation dose. When cells were exposed to room air (normoxia) for 1 day and 95% O2 (hyperoxia) for 1, 2, 3, 4, and 5 days, data indicated that hyperoxia caused time-dependent increases in levels of (a) single strand breaks, (b) double strand breaks, and (c) 8-oxoguanine. Decreased DNA methylation also was observed at day 5 of hyperoxic exposure, suggesting that hyperoxia-induced DNA damage can influence patterns of DNA methylation in a lung-derived cell line.     

Regulation of cyclooxygenase-2 by nitric oxide in activated hepatic macrophages during acute endotoxemia

Eicosanoids generated via cyclooxygenase-2 (COX-2) and nitric oxide produced from inducible nitric oxide synthase (NOSII) have been implicated in endotoxin-induced tissue injury. In the present studies, we characterized COX-2 and NOSII activity in rat hepatic macrophages and their interaction during acute endotoxemia. Kupffer cells from control animals were found to constitutively express COX-2 and NOSII mRNA and protein. Whereas treatment of the cells with lipopolysaccharide (LPS) and/or interferon-gamma (IFN-gamma) had no major effect on COX-2, NOSII expression increased. Induction of acute endotoxemia resulted in a rapid and transient increase in constitutive COX-2 expression and prostaglandin E2 (PGE2) production by liver macrophages as well as NOSII expression and nitric oxide release. Cells from endotoxin-treated rats were also sensitized to generate more nitric oxide and express increased NOSII in response to LPS and IFN-gamma. Inhibition of NOSII with aminoguanidine reduced COX-2 mRNA and protein expression as well as PGE2 production by activated macrophages from endotoxemic, but not control animals. In contrast, SC236, a specific COX-2 inhibitor, had no effect on NOSII mRNA or protein levels or on nitric oxide production by hepatic macrophages, even after endotoxin administration. These data suggest that activation of COX-2 may be important in the pathophysiological response of hepatic macrophages to endotoxin. Moreover, nitric oxide is involved in regulating COX-2 in activated liver macrophages during acute endotoxemia.     

Rules for the classification of younger children with nonverbal learning disabilities and basic phonological processing disabilities.

Rules for the classification of Nonverbal Learning Disabilities (NLD) and Basic Phonological Processing Disabilities (BPPD) that had been generated and tested on older children (ages 9-15) were applied to younger children (ages 7-8). The goal was to evaluate the applicability of these classification rules for a younger population with NLD and BPPD, and to make revisions if necessary. These rules were used to differentiate these two subtypes of learning disabilities using levels and patterns of performance on motor/psychomotor, tactile/perceptual, visual-spatial, auditory-perceptual, problem solving, and language measures. An experienced child-clinical neuropsychologist classified each child. Only those children who received a classification of NLD or BPPD by the neuropsychologist and those who met criteria for definite or probable NLD and BPPD as defined by the rules were used in this study. Revisions were made to these rules for younger children. Revised rules allow for their use as a source of information to assist a clinician in deciding whether a comprehensive neuropsychological evaluation would be valuable. They may also be useful for research purposes.     

Anterior uveitis and congenital fibrosis of the extraocular muscles in a patient with Noonan syndrome

We describe a patient with Noonan syndrome who presented with Human Leukocyte Antigen B27-associated recurrent acute anterior uveitis and manifestations of congenital fibrosis of the extraocular muscles, which has not been reported before.     

Influence of age on iminodipropionitrile-induced vestibular and neurobehavioral toxicities in rats

A direct association between aging and drug-induced dyskinesia has been reported by several investigators. Iminiodipropionitrile (IDPN), a prototype nitrile compound produces a motor syndrome in rodents, which resembles neuroleptic drug induced dyskinesia. In this investigation attempt has been made to study the effect of age on IDPN induced vestibular hair cell degeneration and resulting dyskinetic syndrome. Male Wistar rats aged 3, 6 and 12 weeks received IDPN in the doses of 0, 200 and 400 mg/kg, intraperitoneally for 3 consecutive days. IDPN-induced dyskinesia was assessed using a behavioral testing battery on days 3, 4, 5, 6, 7, 14, 21 and 28. The rats were sacrificed on day 28; temporal bones were excised for vestibular histopathology and sera were collected for measuring the indices of oxidative stress (glutathione and conjugated dienes). IDPN in the dose of 200 mg/kg produced dyskinesia in 12 weeks old rats, but failed to do so in 3 and 6 weeks old rats. The high dose of IDPN (400 mg/kg) caused dyskinesia in all age groups, however, its onset and severity were age-dependent. Older rats showed an early onset and significantly high incidence of dyskinesia as compared to younger rats. The susceptibility of rats to IDPN-induced behavioral deficits was proportional to oxidative stress and degeneration of sensory hair cells in the crista ampullaris.     

Quantitative assessment of the biological effects of follicle regulatory protein on dihydrotestosterone-maintained spermatogenesis in hypophysectomized rat

Follicle regulatory protein (FRP) isolated from porcine ovarian follicles influences folliculogenesis through a paracrine mechanism. A similar protein has been found in the testes and seems to have some inhibitory effects on spermatogenesis when administered to intact male experimental animals. On the basis of female and male studies, it has been ascertained that the effects of FRP are at the level of gonads and not the pituitary or the hypothalamus. In the studies with intact males it was not possible to determine the exact site of FRP action on the testes. Dihydrotestosterone (DHT) has been shown to maintain spermatogenesis in hypophysectomized rats. In order to determine if the inhibitory effects of FRP are at steps prior to the formation of DHT, FRP was administered to hypophysectomized rats that were injected with DHT. Groups of adult rats were hypophysectomized and treated daily with FRP, DHT, FRP + DHT, or vehicle alone for 30 days. At necropsy, body, testes, prostate glands, and seminal vesicle weights were recorded. One testis and sexual accessory glands were fixed for histological evaluation. The contralateral testis was decapsulated, six 2 mm segments of seminiferous tubules, representing defined stages of spermatogenesis, were isolated by transillumination-assisted microdissection, and spermatogenic cells were quantified by DNA flow cytometry. Histologically, the seminiferous tubules of vehicle-treated hypophysectomized controls showed advanced regression. Rats treated with FRP alone showed similar degeneration. On the other hand, rats treated with DHT showed maintenance of spermatogenesis comparable to normal controls. The testes of rats treated with FRP + DHT were indistinguishable from those treated with DHT only. Flow cytometric quantification of germinal cells from all groups confirmed the histological findings. In this study FRP did not exert deleterious effects on DHT-maintained spermatogenesis. This finding suggests that the inhibitory effects of FRP on spermatogenesis in intact animals may not be a direct effect on spermatogenic cells but may impair androgen action or production or DHT formation.     

A Novel Locus for Ectodermal Dysplasia of Hairs, Nails and Teeth Type Maps to Chromosome 18q22.1–22.3

Ectodermal dysplasias (EDs) are developmental disorders affecting tissues of ectodermal origin including hair, nails, teeth and sweat glands. Ectodermal dysplasia of hair, nails and teeth is a rare type of congenital disorder characterized by sparse and thin hair, dystrophic finger-and toenails and missing and abnormal teeth. In an effort to understand the molecular basis of this form of ED a family of Pakistani origin with an autosomal recessive pattern of inheritance was ascertained from a remote region in Pakistan. The clinical features of the affected individuals included thin and fine hair on the scalp, dystrophic and flat nails, absent or sparse eyebrows and eyelashes, missing and abnormal teeth, and thin body hair. A human genome scan carried out using microsatellite markers mapped the disease locus in this family to chromosome 18q22.1–18q22.3. A maximum two-point LOD score of 2.73 (θ= 0.0) was obtained at marker D18S541. Multipoint linkage analysis resulted in a maximum LOD score of 3.42 obtained with several markers, including D18S1125, ATA82B02, D18S848, D18S488, D18S1091, and D18S485, which supported the linkage. The linkage interval is flanked by markers D18S857 and D18S815, which corresponds to a region of 17.32 cM according to Rutgers combined linkage and physical map (build 36). This region covers 8.63 Mb according to the sequence-based physical map. Three candidate genes, CDH7, CDH19 and ZNF407 , from the linkage interval were sequenced and found to be negative for functional sequence variants. This study is the first step towards the identification of a gene involved in hair, nails and teeth type ED.