Mutations in C10orf11, a Melanocyte-Differentiation Gene,Cause Autosomal-Recessive Albinism

Autosomal-recessive albinism is a hypopigmentation disorder with a broad phenotypic range. A substantial fraction of individuals with albinism remain genetically unresolved, and it has been hypothesized that more genes are to be identified. By using homozygosity mapping of an inbred Faroese family, we identified a 3.5 Mb homozygous region (10q22.2–q22.3) on chromosome 10. The region contains five protein-coding genes, and sequencing of one of these, C10orf11, revealed a nonsense mutation that segregated with the disease and showed a recessive inheritance pattern. Investigation of additional albinism-affected individuals from the Faroe Islands revealed that five out of eight unrelated affected persons had the nonsense mutation in C10orf11. Screening of a cohort of autosomal-recessive-albinism-affected individuals residing in Denmark showed a homozygous 1 bp duplication in C10orf11 in an individual originating from Lithuania. Immunohistochemistry showed localization of C10orf11 in melanoblasts and melanocytes in human fetal tissue, but no localization was seen in retinal pigment epithelial cells. Knockdown of the zebrafish (Danio rerio) homolog with the use of morpholinos resulted in substantially decreased pigmentation and a reduction of the apparent number of pigmented melanocytes. The morphant phenotype was rescued by wild-type C10orf11, but not by mutant C10orf11. In conclusion, we have identified a melanocyte-differentiation gene, C10orf11, which when mutated causes autosomal-recessive albinism in humans.     

YKL-40 protein expression in the early developing human musculoskeletal system.

YKL-40 is a growth factor for chondrocytes and fibroblasts. The aim was to evaluate YKL-40 expression in the musculoskeletal system during early human development. We studied sections from 15 human embryos [weeks 5.5-8; 7- to 31-mm crown-rump length (CRL)] and 68 fetuses (weeks 9-14; 33- to 105-mm CRL) for YKL-40 protein expression by immunohistochemistry. YKL-40 mRNA expression was evaluated in two human embryos (days 41 and 51). Initially YKL-40 is expressed in all germ layers: ecto-, meso-, and endoderm. YKL-40 mRNA and protein expression are found in tissues of the ecto-, meso-, and endoderm, and YKL-40 protein expression is present during development of cartilage, bone, joints, and muscles. At the cellular level, YKL-40 protein expression is high in tissues characterized by rapid proliferation, marked differentiation, and undergoing morphogenetic changes. Examples of rapid cell proliferation include the chondrogenic inner layer of perichondrium and the osteogenic inner layer of periosteum. Differences in YKL-40 expression during differentiation are found in the chondrogenic and osteogenic cell lineages. The initial shaping of cartilage and bone models and joints is concomitant with a strong outline of YKL-40-positive cells. This indicates that YKL-40 is associated with cell proliferation, differentiation, and tissue morphogenesis during development of the human musculoskeletal system.     

Linkage analysis of juvenile myoclonic epilepsy and microsatellite loci spanning 61 cM of human chromosome 6p in 19 nuclear pedigrees provides no evidence for a susceptibility locus in this region.

Linkage analysis in separately ascertained families of probands with juvenile myoclonic epilepsy (JME) has previously provided evidence both for and against the existence of a locus (designated "EJM1"), on chromosome 6p, predisposing to a trait defined as either clinical JME, its associated electroencephalographic abnormality, or idiopathic generalized epilepsy. Linkage analysis was performed in 19 families in which a proband and at least one first- or two second-degree relatives have clinical JME. Family members were typed for seven highly polymorphic microsatellite markers on chromosome 6p: D6S260, D6S276, D6S291, D6S271, D6S465, D6S257, and D6S254. Pairwise and multipoint linkage analysis was carried out under the assumptions of autosomal dominant inheritance at 70% and 50% penetrance and autosomal recessive inheritance at 70% and 50% penetrance. No significant evidence in favor of linkage to the clinical trait of JME was obtained for any locus. The region formally excluded (LOD score < -2) by using multipoint analysis varies depending on the assumptions made concerning inheritance parameters and the proportion of linked families, alpha-that is, the degree of locus heterogeneity. Further analysis either classifying all unaffected individuals as unknown or excluding a subset of four families in which pyknoleptic absence seizures were present in one or more individuals did not alter these conclusions.     

SGP28, a novel matrix glycoprotein in specific granules of human neutrophils with similarity to a human testis-specific gene product and to a rodent sperm-coating glycoprotein

A novel 28 kDa glycoprotein was purified from exocytosed material from human neutrophils and its primary structure partially determined. Degenerate oligonucleotide primers were used to amplify cDNA clones from a human bone marrow cDNA library. The deduced 245 amino acid sequence of the 2124 bp full-length cDNA showed high degrees of similarity to the deduced sequences of the human gene TPX-1 and of sperm coating glycoprotein from rat and mouse. Subcellular fractionation of human neutrophils indicated that the protein is localized in specific granules. The protein was named SGP28 (specific granule protein of 28 kDa).     

Molecular cloning of a cDNA of a camptothecin-resistant human DNA topoisomerase I and identification of mutation sites.

Camptothecin (CPT), a plant alkaloid with antitumor activity, is a specific inhibitor of eukaryotic DNA topoisomerase I. We have previously isolated and characterized a CPT-resistant topoisomerase I isolated from a CPT-resistant human leukemia cell line, CPT-K5. cDNA clones of topoisomerase I were isolated from the CPT-resistant and the parental CPT-sensitive cell lines, respectively. Sequencing of the clones identified two mutations in the cDNA isolated from the resistant cells, which cause amino acid changes from aspartic acid to glycine at residues 533 and 583 of the parental topoisomerase I. When the CPT-K5 topoisomerase I was expressed in E. coli as a fusion protein with Staphylococcal Protein A fragment, the activity was resistant to CPT at a dose level up to 125 microM, whereas the parental fusion protein was sensitive to CPT as low as 1 microM. The resistance index (greater than 125) of the CPT-K5 fusion topoisomerase I is similar to that of the native CPT-K5 topoisomerase I. These results indicate that either or both of the two amino acid changes identified in the mutant enzyme is responsible for the resistance to CPT.     

Possible epithelial sodium channels visualized by freeze-fracture

The coprodeum is a very efficient Na⁺-retaining epithelium. Coprodeum from birds on a high Na⁺ diet has virtually no ion transport, while an Amiloride-sensitive Na⁺ absorption of 10–12 μ equiv·cm^?2·h^?1 is induced in the coprodeal epithelium from birds on a low Na⁺ diet. Both measurements of the Na⁺ influx and Na⁺-diffusion potentials across the luminal cell membrane have revealed a selective opening of this membrane to Na⁺ in birds on a low Na⁺ diet. Freeze-fracture P faces of the luminal membrane in coprodea taken from birds on a low Na⁺ diet have rod-shaped particles, $\text{100 × 240}\text{A}\text{?}$, in more than 20% of the principal cells. Rod-shaped particles appear in less than 1% of these cells in coprodea from high Na⁺-diet birds. Thus a low Na⁺ diet induces rod-shaped particles in the luminal cell membrane of the hen coprodeum. These new particles may function as Na⁺-channels mediating the increased Na⁺-influx across the apical cell membrane.     

Conformational studies on polynucleotide chains. V. A comparison between the quantum-mechanical and the consistent force field approach

Consistent force field (CFF) calculations were performed for the sugar–phosphate–sugar fragment, taken as a model of the polynucleotide backbone. The potential-energy-function is the sum of four contributions, accounting for bond and angle deformation, torsional motions, and nonbonded interactions. Both deoxyribose and ribose systems, with either C(2′)-endo or C(3′)-endo puckering in the starting geometry of ribose rings, were considered. A fair number of minima of the conformational-energy hypersurface were found. Although the numerical method employed in the CFF context cannot solve the problem of finding the global minimum in a definite way, one of the final conformations has a total energy much more attractive than the others, and may be regarded as the most stable conformation attainable with our potential-energy function. The energy-minimization affects the puckering of the first ribose ring differently from that of the second: in general, for the C(2′)-endo system the second ring retains its starting conformation (Ψ′ = 152°), while in the first the Ψ′ is modified by up to 70°; the opposite occurs for the C(3′)-endo system. This is explained by the different positions of the two rings relative to the phosphate group.     

The involvement of protein kinase C in exocytosis in mast cells.

Diacylglycerol generated from inositolphospholipid hydrolysis and tumor-promoting phorbol esters stimulate protein kinase C. The synthetic diacylglycerol 1-oleoyl-2-acetyl-rac-glycerol and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) have been used in pure rat peritoneal mast cells. Both caused histamine release associated with exocytosis. The release by the stimulation of protein kinase C alone in the absence of secretagogues was slow although up to 50% of the histamine content was released by TPA in 120 min. Remarkable potentiation of histamine release was observed when the mast cells were preincubated with TPA before exposure to the calcium ionophore A23187. The potentiation of histamine release corresponded with an intensification of exocytosis. The potentiation is consistent with a participation of protein kinase C in the secretory process. An inhibitory effect due to protein kinase C activity was also demonstrated using TPA and mast cells from sensitized rats. When sensitized mast cells preincubated with 50 nM TPA for 5 min were exposed to the antigen, the histamine release was substantially reduced compared to the sum of the release by the antigen and TPA or by the antigen alone. There was a corresponding decrease in exocytosis. The inhibition of exocytosis and histamine release seems to reflect a regulatory function of protein kinase C for the termination of the response, as demonstrated in other types of cells apparently acting through an inhibition of inositolphospholipid hydrolysis.