NLRP1 promotes tumor growth by enhancing inflammasome activation and suppressing apoptosis in metastatic melanoma.

Inflammasomes are mediators of inflammation, and constitutively activated NLRP3 inflammasomes have been linked to interleukin-1ß (IL-1ß)-mediated tumorigenesis in human melanoma. Whereas NLRP3 regulation of caspase-1 activation requires the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD (caspase recruitment domain)), caspase-1 activation by another danger-signaling sensor NLRP1 does not require ASC because NLRP1 contains a C-terminal CARD domain that facilitates direct caspase-1 activation via CARD-CARD interaction. We hypothesized that NLRP1 has additional biological activities besides IL-1ß maturation and investigated its role in melanoma tumorigenesis. NLRP1 expression in melanoma was confirmed by analysis of 216 melanoma tumors and 13 human melanoma cell lines. Unlike monocytic THP-1 cells with prominent nuclear localization of NLRP1, melanoma cells expressed NLRP1 mainly in the cytoplasm. Knocking down NLRP1 revealed a tumor-promoting property of NLRP1 both in vitro and in vivo. Mechanistic studies showed that caspase-1 activity, IL-1ß production, IL-1ß secretion and nuclear factor-kB activity were reduced by knocking down of NLRP1 in human metastatic melanoma cell lines 1205Lu and HS294T, indicating that NLRP1 inflammasomes are active in metastatic melanoma. However, unlike previous reports showing that NLRP1 enhances pyroptosis in macrophages, NLRP1 in melanoma behaved differently in the context of cell death. Knocking down NLRP1 increased caspase-2, -9 and -3/7 activities and promoted apoptosis in human melanoma cells. Immunoprecipitation revealed interaction of NLRP1 with CARD-containing caspase-2 and -9, whereas NLRP3 lacking a CARD motif did not interact with the caspases. Consistent with these findings, NLRP1 activation but not NLRP3 activation reduced caspase-2, -9 and -3/7 activities and provided protection against apoptosis in human melanoma cells, suggesting a suppressive role of NLRP1 in caspase-3/7 activation and apoptosis via interaction with caspase-2 and -9. In summary, we showed that NLRP1 promotes melanoma growth by enhancing inflammasome activation and suppressing apoptotic pathways. Our study demonstrates a tumor-promoting role of NLRP1 in cancer cells.

Genetic structure of phenotypic robustness in the collaborative cross mouse diallel panel.

Developmental stability and canalization describe the ability of developmental systems to minimize phenotypic variation in the face of stochastic micro-environmental effects, genetic variation and environmental influences. Canalization is the ability to minimize the effects of genetic or environmental effects, whereas developmental stability is the ability to minimize the effects of micro-environmental effects within individuals. Despite much attention, the mechanisms that underlie these two components of phenotypic robustness remain unknown. We investigated the genetic structure of phenotypic robustness in the collaborative cross (CC) mouse reference population. We analysed the magnitude of fluctuating asymmetry (FA) and among-individual variation of cranial shape in reciprocal crosses among the eight parental strains, using geometric morphometrics and a diallel analysis based on a Bayesian approach. Significant differences among genotypes were found for both measures, although they were poorly correlated at the level of individuals. An overall positive effect of inbreeding was found for both components of variation. The strain CAST/EiJ exerted a positive additive effect on FA and, to a lesser extent, among-individual variance. Sex- and other strain-specific effects were not significant. Neither FA nor among-individual variation was associated with phenotypic extremeness. Our results support the existence of genetic variation for both developmental stability and canalization. This finding is important because robustness is a key feature of developmental systems. Our finding that robustness is not related to phenotypic extremeness is consistent with theoretical work that suggests that its relationship to stabilizing selection is not straightforward.

The genetics and epigenetics of orofacial clefts.

Orofacial clefts (cleft lip, cleft palate) are among the most common of all major birth defects, but very little is known about their causation. Genetic factors are thought to play a major role, and there has been considerable recent effort to map and identify genes that constitute risk factors for clefts. This review will put into perspective the frequently-conflicting results of these studies.

Duplication of 15q11.2-q14, including the P gene, in a woman with generalized skin hyperpigmentation.

We describe a woman with 15q11.2-q14 duplication who had clinical manifestations of proximal 15q trisomy and hyperpigmentation. Within this region, the P gene, located at chromosome segment 15q11.2-q12, is associated with oculocutaneous albinism type II (OCA2) and with hypopigmentation in the Prader-Willi and Angelman chromosome 15q deletion syndromes. We therefore hypothesized that in this woman skin hyperpigmentation might result from a duplication of the P gene. We carried out chromosomal and interphase fluorescence in situ hybridization (I-FISH) analyses, and determined that the P gene is duplicated in this woman. Our findings demonstrate that trisomy of the P gene can be associated with skin hyperpigmentation.

The gene mutated in cocoa mice, carrying a defect of organelle biogenesis, is a homologue of the human Hermansky-Pudlak syndrome-3 gene.

Hermansky-Pudlak syndrome (HPS) is a group of human disorders of organelle biogenesis characterized by defective synthesis of melanosomes, lysosomes, and platelet dense granules. In the mouse, at least 15 loci are associated with mutant phenotypes similar to human HPS. We have identified the gene mutated in cocoa (coa) mice, which is associated with an HPS-like mutant phenotype and thus represents a strong candidate for human HPS. Analysis of coa-mutant mice and cultured coa-mutant mouse melanocytes indicates that the normal coa gene product is involved in early stages of melanosome biogenesis and maturation.

Mutation of PVRL1 is associated with sporadic, non-syndromic cleft lip/palate in northern Venezuela.

Non-syndromic cleft lip with or without cleft palate (CL/P, MIM 119530) is among the most common of major birth defects. Homozygosity for a nonsense mutation of PVRL1, W185X, results in an autosomal recessive CL/P syndrome on Margarita Island, CLPED1 (ref. 1). Here we demonstrate highly significant association between heterozygosity for this mutation and sporadic, non-syndromic CL/P in northern Venezuela.

The molecular basis of oculocutaneous albinism type 1 (OCA1): sorting failure and degradation of mutant tyrosinases results in a lack of pigmentation.

Oculocutaneous albinism type 1 (OCA1) is an autosomal recessive disease resulting from mutations of the tyrosinase gene (TYR). To elucidate the molecular basis of OCA1 phenotypes, we analysed the early processing and maturation of several different types of mutant tyrosinase with various degrees of structural abnormalities (i.e. two large deletion mutants, two missense mutants that completely destroy catalytic function and three missense mutants that have a temperature-sensitive phenotype). When expressed in COS7 cells, all mutant tyrosinases were sensitive to endoglycosidase H digestion, and immunostaining showed their localization in the endoplasmic reticulum (ER) and their failure to be sorted further to their target organelles. Pulse-chase experiments showed that all mutant tyrosinases were retained by calnexin in the ER and that they were degraded at similarly rapid rates, which coincided with their dissociation from calnexin. Temperature-sensitive mutant enzymes were sorted more efficiently at 31 degrees C than at 37 degrees C, and their degradation was accelerated at 37 degrees C compared with 31 degrees C. Thus in contrast to the current concept that mutant tyrosinases are transported to melanosomes but are functionally inactive there, our results suggest that mutant tyrosinases may not be transported to melanosomes in the first place. We conclude that a significant component of mutant tyrosinase malfunction in OCA1 results from their retention and degradation in the ER compartment. This quality-control process is highly sensitive to minimal changes in protein folding, and so even relatively minor mutations in peripheral sequences of the enzyme not involved with catalytic activity may result in a significant reduction of functional enzyme in melanosomes.

Mutations of PVRL1, encoding a cell-cell adhesion molecule/herpesvirus receptor, in cleft lip/palate-ectodermal dysplasia.

Cleft lip, with or without cleft palate (CL/P), is one of the most common birth defects, occurring in 0.4 to 2.0 per 1,000 infants born alive. Approximately 70% of CL/P cases are non-syndromic (MIM 119530), but CL/P also occurs in many single-gene syndromes, each affecting a protein critical for orofacial development. Here we describe positional cloning of the gene responsible for an autosomal recessive CL/P-ectodermal dysplasia (ED) syndrome (CLPED1; previously ED4; ref. 2), which we identify as PVRL1, encoding nectin-1, an immunoglobulin (Ig)-related transmembrane cell-cell adhesion molecule that is part of the NAP cell adhesion system. Nectin-1 is also the principal cell surface receptor for alpha-herpesviruses (HveC; ref. 7), and the high frequency of CLPED1 on Margarita Island in the Caribbean Sea might result from resistance of heterozygotes to infection by these viruses.

Hermansky-Pudlak syndrome and pale ear: melanosome-making for the millennium.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder characterized principally by oculocutaneous albinism, a bleeding tendency, and a ceroid-lipofuscin lysosomal storage disease. These clinical manifestations of HPS are associated with defects of multiple cytoplasmic organelles--melanosomes, platelet granules, and lysosomes--suggesting that the HPS gene product is involved in some shared feature of the biogenesis or functions of these diverse organelles. The HPS gene has been cloned, and a number of pathologic mutations of the gene have been identified. Functional studies indicate that the HPS protein is part of a high-molecular weight complex involved in the biogenesis of early melanosomes. Additional disorders with similarities to HPS have been identified in man, mouse, flies, and yeast, and it is rapidly becoming clear that understanding these disorders will shed new light on the mechanisms by which cells traffic newly synthesized proteins through the cytoplasm to assemble functional organelles.

The Hermansky-Pudlak syndrome (HPS) protein is part of a high molecular weight complex involved in biogenesis of early melanosomes.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder in which oculocutaneous albinism, bleeding tendency and a ceroid-lipofuscin lysosomal storage disease result from defects of multiple cytoplasmic organelles: melanosomes, platelet dense granules and lysosomes. The HPS polypeptide, a 700 amino acid protein which is unrelated to any known proteins, is likely to be involved in the biogenesis of these different organelles. Here, we show that HPS is a non-glycosylated, non-membrane protein which is a component of two distinct high molecular weight complexes. In non-melanotic cells the HPS protein is contained almost entirely in an approximately 200 kDa complex that is widely distributed throughout the cytosol. In melanotic cells the HPS protein is partitioned between this cytosolic complex and a >500 kDa complex that appears to consist of the approximately 200 kDa complex in association with membranous components. Subcellular fractionation, immunofluorescence and immunoelectron microscopy studies indicate that the membrane-associated HPS complex of melanotic cells is associated with tubulovesicular structures, small non-coated vesicles, and nascent and early-stage melanosomes. These findings suggest that the HPS complex is involved in the biogenesis of early melanosomes.

Multi-organellar disorders of pigmentation: intracellular traffic jams in mammals, flies and yeast.

Several different mutant genes in humans, mice and Drosophila, most of which were identified initially on the basis of reduced pigmentation, have been associated with defects of multiple cytoplasmic organelles - melanosomes, lysosomes and granules. Recent discoveries show that several of these mutations directly affect components in the pathway of organelle-specific protein trafficking, and provide new insights into the relationships of these pathways in mammals, flies and yeast.

Linkage disequilibrium mapping of the gene for Margarita Island ectodermal dysplasia (ED4) to 11q23.

Margarita Island ectodermal dysplasia (ED4) is an autosomal recessive disorder characterized by unusual facies, dental anomalies, hypotrichosis, palmoplantar hyperkeratosis and onychodysplasia, syndactyly, and cleft lip/cleft palate. We have used an affected-only DNA-pooling strategy to carry out linkage disequilibrium mapping of the ED4 gene to 11q23. Haplotype analysis of four complex Margarita Island ED4 families localized the ED4 gene to an approximately 1-2-Mb interval spanned by just two YACs.

A gene for autosomal dominant hypohidrotic ectodermal dysplasia (EDA3) maps to chromosome 2q11-q13.

Autosomal dominant hypohidrotic ectodermal dysplasia (ADHED) is a disorder characterized by fine, slow-growing scalp and body hair, sparse eyebrows and eyelashes, decreased sweating, hypodontia, and nail anomalies. By genetic linkage analysis of a large ADHED kindred, we have mapped a gene for ADHED (EDA3) to the proximal long arm of chromosome 2 (q11-q13). Obligate recombinations localize EDA3 to an approximately 9-cM interval between D2S1321 and D2S308, with no apparent recombinations with markers D2S1343, D2S436, D2S293, D2S1894, D2S1784, D2S1890, D2S274, and CHLC.GAAT11C03.

Mutation analysis of patients with Hermansky-Pudlak syndrome: a frameshift hot spot in the HPS gene and apparent locus heterogeneity.

Hermansky-Pudlak syndrome (HPS) is a rare, autosomal recessive disorder in which oculocutaneous albinism, bleeding, and lysosomal ceroid storage result from defects of multiple cytoplasmic organelles-melanosomes, platelet-dense granules, and lysosomes. As reported elsewhere, we mapped the human HPS gene to chromosome segment 10q23, positionally cloned the gene, and identified three pathologic mutations of the gene, in patients from Puerto Rico, Japan, and Europe. Here, we describe mutation analysis of 44 unrelated Puerto Rican and 24 unrelated non-Puerto Rican HPS patients. A 16-bp frameshift duplication, the result of an apparent founder effect, is nearly ubiquitous among Puerto Rican patients. A frameshift at codon 322 may be the most frequent HPS mutation in Europeans. We also describe six novel HPS mutations: a 5' splice-junction mutation of IVS5, three frameshifts, a nonsense mutation, and a one-codon in-frame deletion. These mutations define an apparent frameshift hot spot at codons 321-322. Overall, however, we detected mutations in the HPS gene in only about half of non-Puerto Rican patients, and we present evidence that suggests locus heterogeneity for HPS.

Genetic defects in Chediak-Higashi syndrome and the beige mouse.

Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive, multisystem disorder in which severe immune deficits are accompanied by abnormalities of pigmentation, blood clotting, and neurologic function. There is no specific treatment, and without bone marrow transplantation, most patients succumb to frequent bacterial infections or to a lymphoproliferative syndrome that appears to result principally from lack of natural killer cell function. Disorders similar to human CHS occur in many mammalian species, the most important being the beige mouse, long considered a likely homologue of human CHS. This supposition has recently been confirmed by the mapping, cloning, and mutation analysis of the homologous human CHS1 and mouse beige genes. Identification of the human CHS1 gene, and the availability of a ready mouse model for human CHS, will likely facilitate investigation of the disease pathophysiology and the development of novel and specific treatments for the disorder.