(1/1138) UCP4, a novel brain-specific mitochondrial protein that reduces membrane potential in mammalian cells.
Uncoupling proteins (UCPs) are a family of mitochondrial transporter proteins that have been implicated in thermoregulatory heat production and maintenance of the basal metabolic rate. We have identified and partially characterized a novel member of the human uncoupling protein family, termed uncoupling protein-4 (UCP4). Protein sequence analyses showed that UCP4 is most related to UCP3 and possesses features characteristic of mitochondrial transporter proteins. Unlike other known UCPs, UCP4 transcripts are exclusively expressed in both fetal and adult brain tissues. UCP4 maps to human chromosome 6p11.2-q12. Consistent with its potential role as an uncoupling protein, UCP4 is localized to the mitochondria and its ectopic expression in mammalian cells reduces mitochondrial membrane potential. These findings suggest that UCP4 may be involved in thermoregulatory heat production and metabolism in the brain. (+info)
(2/1138) NKp44, a triggering receptor involved in tumor cell lysis by activated human natural killer cells, is a novel member of the immunoglobulin superfamily.
Surface receptors involved in natural killer (NK) cell triggering during the process of tumor cell lysis have recently been identified. Of these receptors, NKp44 is selectively expressed by IL-2- activated NK cells and may contribute to the increased efficiency of activated NK cells to mediate tumor cell lysis. Here we describe the molecular cloning of NKp44. Analysis of the cloned cDNA indicated that NKp44 is a novel transmembrane glycoprotein belonging to the Immunoglobulin superfamily characterized by a single extracellular V-type domain. The charged amino acid lysine in the transmembrane region may be involved in the association of NKp44 with the signal transducing molecule killer activating receptor-associated polypeptide (KARAP)/DAP12. These molecules were found to be crucial for the surface expression of NKp44. In agreement with data of NKp44 surface expression, the NKp44 transcripts were strictly confined to activated NK cells and to a minor subset of TCR-gamma/delta+ T lymphocytes. Unlike genes coding for other receptors involved in NK cell triggering or inhibition, the NKp44 gene is on human chromosome 6. (+info)
(3/1138) The predisposition to type 1 diabetes linked to the human leukocyte antigen complex includes at least one non-class II gene.
The human leukocyte antigen (HLA) complex, encompassing 3.5 Mb of DNA from the centromeric HLA-DPB2 locus to the telomeric HLA-F locus on chromosome 6p21, encodes a major part of the genetic predisposition to develop type 1 diabetes, designated "IDDM1." A primary role for allelic variation of the class II HLA-DRB1, HLA-DQA1, and HLA-DQB1 loci has been established. However, studies of animals and humans have indicated that other, unmapped, major histocompatibility complex (MHC)-linked genes are participating in IDDM1. The strong linkage disequilibrium between genes in this complex makes mapping a difficult task. In the present paper, we report on the approach we have devised to circumvent the confounding effects of disequilibrium between class II alleles and alleles at other MHC loci. We have scanned 12 Mb of the MHC and flanking chromosome regions with microsatellite polymorphisms and analyzed the transmission of these marker alleles to diabetic probands from parents who were homozygous for the alleles of the HLA-DRB1, HLA-DQA1, and HLA-DQB1 genes. Our analysis, using three independent family sets, suggests the presence of an additional type I diabetes gene (or genes). This approach is useful for the analysis of other loci linked to common diseases, to verify if a candidate polymorphism can explain all of the association of a region or if the association is due to two or more loci in linkage disequilibrium with each other. (+info)
(4/1138) Murine p38-delta mitogen-activated protein kinase, a developmentally regulated protein kinase that is activated by stress and proinflammatory cytokines.
The p38 mitogen-activated protein kinases (MAPK) play a crucial role in stress and inflammatory responses and are also involved in activation of the human immunodeficiency virus gene expression. We have isolated the murine cDNA clones encoding p38-delta MAPK, and we have localized the p38-delta gene to mouse chromosome 17A3-B and human chromosome 6p21.3. By using Northern and in situ hybridization, we have examined the expression of p38-delta in the mouse adult tissues and embryos. p38-delta was expressed primarily in the lung, testis, kidney, and gut epithelium in the adult tissues. Although p38-delta was expressed predominantly in the developing gut and the septum transversum in the mouse embryo at 9.5 days, its expression began to be expanded to many specific tissues in the 12.5-day embryo. At 15.5 days, p38-delta was expressed virtually in most developing epithelia in embryos, suggesting that p38-delta is a developmentally regulated MAPK. Interestingly, p38-delta and p38-alpha were similar serine/threonine kinases but differed in substrate specificity. Overall, p38-delta resembles p38-gamma, whereas p38-beta resembles p38-alpha. Moreover, p38-delta is activated by environmental stress, extracellular stimulants, and MAPK kinase-3, -4, -6, and -7, suggesting that p38-delta is a unique stress-responsive protein kinase. (+info)
(5/1138) A genome search identifies major quantitative trait loci on human chromosomes 3 and 4 that influence cholesterol concentrations in small LDL particles.
Small, dense LDL particles are associated with increased risk of cardiovascular disease. To identify the genes that influence LDL size variation, we performed a genome-wide screen for cholesterol concentrations in 4 LDL size fractions. Samples from 470 members of randomly ascertained families were typed for 331 microsatellite markers spaced at approximately 15 cM intervals. Plasma LDLs were resolved by using nondenaturing gradient gel electrophoresis into 4 fraction sizes (LDL-1, 26.4 to 29.0 nm; LDL-2, 25.5 to 26.4 nm; LDL-3, 24.2 to 25.5 nm; and LDL-4, 21.0 to 24.2 nm) and cholesterol concentrations were estimated by staining with Sudan Black B. Linkage analyses used variance component methods that exploited all of the genotypic and phenotypic information in the large extended pedigrees. In multipoint linkage analyses with quantitative trait loci for the 4 fraction sizes, only LDL-3, a fraction containing small LDL particles, gave peak multipoint log10 odds in favor of linkage (LOD) scores that exceeded 3.0, a nominal criterion for evidence of significant linkage. The highest LOD scores for LDL-3 were found on chromosomes 3 (LOD=4.1), 4 (LOD=4.1), and 6 (LOD=2.9). In oligogenic analyses, the 2-locus LOD score (for chromosomes 3 and 4) increased significantly (P=0.0012) to 6.1, but including the third locus on chromosome 6 did not significantly improve the LOD score (P=0.064). Thus, we have localized 2 major quantitative trait loci that influence variation in cholesterol concentrations of small LDL particles. The 2 quantitative trait loci on chromosomes 3 and 4 are located in regions that contain the genes for apoD and the large subunit of the microsomal triglyceride transfer protein, respectively. (+info)
(6/1138) Linkage of Crohn's disease to the major histocompatibility complex region is detected by multiple non-parametric analyses.
BACKGROUND: There is evidence for genetic susceptibility to Crohn's disease, and a tentative association with tumour necrosis factor (TNF) and HLA class II alleles. AIMS: To examine the potential of genetic linkage between Crohn's disease and the MHC region on chromosome 6p. METHODS: TNF microsatellite markers and, for some families, additional HLA antigens were typed for 323 individuals from 49 Crohn's disease multiplex families to generate informative haplotypes. Non-parametric linkage analysis methods, including sib pair and affected relative pair methods, were used. RESULTS: Increased sharing of haplotypes was observed in affected sib pairs: 92% (48/52) shared one or two haplotypes versus an expected 75% if linkage did not exist (p=0.004). After other affected relative pairs were included, the significance level reached 0.001. The mean proportion of haplotype sharing was increased for both concordant affected (pi=0.60, p=0.002) and unaffected sib pairs (pi=0.58, p=0. 031) compared with the expected value (pi=0.5). In contrast, sharing in discordant sib pairs was significantly decreased (pi=0.42, p=0. 007). Linear regression analysis using all three types of sib pairs yielded a slope of -0.38 at p=0.00003. It seemed that the HLA effect was stronger in non-Jewish families than in Jewish families. CONCLUSIONS: All available analytical methods support linkage of Crohn's disease to the MHC region in these Crohn's disease families. This region is estimated to contribute approximately 10-33% of the total genetic risk to Crohn's disease. (+info)
(7/1138) Genetic linkage of IgA deficiency to the major histocompatibility complex: evidence for allele segregation distortion, parent-of-origin penetrance differences, and the role of anti-IgA antibodies in disease predisposition.
Immunoglobulin A (IgA) deficiency (IgAD) is characterized by a defect of terminal lymphocyte differentiation, leading to a lack of IgA in serum and mucosal secretions. Familial clustering, variable population prevalence in different ethnic groups, and a predominant inheritance pattern suggest a strong genetic predisposition to IgAD. The genetic susceptibility to IgAD is shared with a less prevalent, but more profound, defect called "common variable immunodeficiency" (CVID). Here we show an increased allele sharing at 6p21 in affected members of 83 multiplex IgAD/CVID pedigrees and demonstrate, using transmission/diseqilibrium tests, family-based associations indicating the presence of a predisposing locus, designated "IGAD1," in the proximal part of the major histocompatibility complex (MHC). The recurrence risk of IgAD was found to depend on the sex of parents transmitting the defect: affected mothers were more likely to produce offspring with IgAD than were affected fathers. Carrier mothers but not carrier fathers transmitted IGAD1 alleles more frequently to the affected offspring than would be expected under random segregation. The differential parent-of-origin penetrance is proposed to reflect a maternal effect mediated by the production of anti-IgA antibodies tentatively linked to IGAD1. This is supported by higher frequency of anti-IgA-positive females transmitting the disorder to children, in comparison with female IgAD nontransmitters, and by linkage data in the former group. Such pathogenic mechanisms may be shared by other MHC-linked complex traits associated with the production of specific autoantibodies, parental effects, and a particular MHC haplotype. (+info)
(8/1138) Suppression of tumorigenicity in human ovarian cancer cell lines is controlled by a 2 cM fragment in chromosomal region 6q24-q25.
Multiple distinct regions of chromosome 6 are frequently affected by losses of heterozygosity in primary human ovarian carcinomas. We introduced a normal human chromosome 6 into HEY and SKOV-3 ovarian carcinoma cell lines using microcell-mediated chromosome transfer techniques to further investigate the role of this chromosome in ovarian tumorigenesis. The exogenous chromosome was stably propagated in the recipient cells based on fluorescence in situ hybridization (FISH) analyses with a chromosome 6 painting probe. The tumorigenicity of HEY and SKOV-3 cells was completely suppressed after transfer of chromosome 6, but not after transfer of a chromosome 11q13-qter fragment used as control. Using 46 polymorphic microsatellite markers, the region bounded by D6S1649 and D6S1564 was found to be commonly deleted in HEY: chromosome 6 tumorigenic revertant clones. The boundaries of the commonly deleted region could be further narrowed down to a 2 cM (based on the Whitehead genetic map) or 0.36 megabase (based on gdb mapping data) region between D6S1637 and D6S1564 after transferring the exogenous chromosome from revertants into mouse L cells and performing allelic deletion mapping studies against this mouse background. We conclude that this region contains a tumor suppressor gene important for the control of ovarian tumor development. (+info)