Faculty Bibliography

Hypohidrotic ectodermal dysplasia (HED), a congenital disorder of teeth, hair, and eccrine sweat glands, is usually inherited as an X-linked recessive trait, although rarer autosomal dominant and recessive forms exist. We have studied males from four families with HED and immunodeficiency (HED-ID), in which the disorder segregates as an X-linked recessive trait. Affected males manifest dysgammaglobulinemia and, despite therapy, have significant morbidity and mortality from recurrent infections. Recently, mutations in IKK-gamma (NEMO) have been shown to cause familial incontinentia pigmenti (IP). Unlike HED-ID, IP affects females and, with few exceptions, causes male prenatal lethality. IKK-gamma is required for the activation of the transcription factor known as 'nuclear factor kappa B' and plays an important role in T and B cell function. We hypothesize that 'milder' mutations at this locus may cause HED-ID. In all four families, sequence analysis reveals exon 10 mutations affecting the carboxy-terminal end of the IKK-gamma protein, a domain believed to connect the IKK signalsome complex to upstream activators. The findings define a new X-linked recessive immunodeficiency syndrome, distinct from other types of HED and immunodeficiency syndromes. The data provide further evidence that the development of ectodermal appendages is mediated through a tumor necrosis factor/tumor necrosis factor receptor-like signaling pathway, with the IKK signalsome complex playing a significant role

The albino (tyrosinase, Tyrc), brown (tyrosinase-related protein 1, Tyrp1b) and slaty (tyrosinase-related protein 2, tyrp2slt) loci are all involved in the regulation of melanogenesis. Phenotypes of inbred mice mutant at two or more of these loci are not always explicable by simple summation of the established or suspected catalytic functions of the gene products. These phenotypes suggest that relationships among the proteins extend beyond the obvious fact that they catalyze different steps in the same melanogenic pathway, and that they may also interact intimately in such a way that a mutation in one impacts the function of the other(s). Previous studies have attributed catalytic activities to each member of this trio; however, it has been difficult to study the proteins individually, either in vivo or in tissues or cells. Therefore, we undertook to transfect the genes, in revealing combinations, into COS-7 cells (which have no melanogenic apparatus of their own) to clarify the interacting functions of their encoded proteins. Specifically, we attempted to evaluate the effects of Tyrp1 and Tyrp2 proteins on tyrosinase protein. We report evidence that Tyrp1 stabilizes tyrosinase, confirming previous observations, and, in addition, demonstrate that Tyrp1 decreases tyrosinase activity. By contrast, Tyrp2 increases tyrosinase activity by stabilizing the protein. We conclude that both Tyrp1 and Tyrp2, in addition to other catalytic functions they may possess, act together to modulate tyrosinase activity

It was recently reported that a majority of hybrids generated in vitro between weakly metastatic mouse Cloudman S91 melanoma cells and human or mouse macrophages showed enhanced metastatic potential (Rachkovsky et al., 1998). With few exceptions, hybrids with enhanced metastatic potential also had elevated basal melanin content, enhanced chemotactic responses to fibroblast-conditioned media, and stronger responsiveness to MSH compared to parental cells. Analyses revealed that altered N-glycosylation in metastatic hybrids could explain the multiple phenotypic changes. Tyrosinase, TRP-2 and LAMP-1 from hybrids migrated more slowly on gels compared to the same proteins from parental melanoma cells, consistent with increased glycosylation. Migration of LAMP-1 from hybrids was similar to that from peritoneal macrophages which also appeared to be more heavily glycosylated than LAMP-1 from Cloudman cells. The incorporation of 3H-glucosamine, as a marker of N-glycosylation, into tyrosinase and LAMP-1 was found to be elevated in hybrids, suppressed by N-glycosylation inhibitors and stimulated by MSH to a greater degree in hybrids compared to parental cells. These results indicate N-glycosylation as an important regulatory pathway for MSH-induced melanogenesis, and further suggest that altered N-linked glycosylation may be an underlying mechanism for regulation of both melanogenesis and metastasis in macrophage x melanoma hybrids

Infantile hemangiomas are the most common tumor of infancy, occurring with an incidence of up to 10% of all births. They are benign but highly proliferative lesions involving aberrant localized growth of capillary endothelium. Although most hemangiomas occur sporadically and as single lesions, or in conjunction with pleiotropic genetic syndromes, we have previously identified six kindreds where hemangiomas appear to segregate as an autosomal dominant trait with high penetrance. Four such families contain affected individuals in three or more generations. In the current study, blood samples from five of these families were collected and used in a whole genome linkage search at 10-cM resolution. We established evidence for linkage to 5q in three families, and evidence for locus heterogeneity. The three 5q-linked families were further genotyped to generate haplotype information and narrow the candidate interval. Based on recombination breakpoint analysis, the interval exists between markers D5S2490 and D5S408, spanning 55 cM, and corresponding to 5q31-33. Using information from affected and unaffected individuals, the interval spans 38 cM between markers D5S1469 and D5S211. Three candidate genes involved with blood vessel growth map to this region: fibroblast growth factor receptor-4 (FGFR4), platelet-derived growth factor receptor-beta (PDG-FRB), and fms-related tyrosine kinase-4 (FLT4). The genes and gene products associated with familial hemangiomas may be involved somatically in the more common sporadic cases

In order to study proteins of the melanosome, we developed a panel of antisera against various protein fractions of melanosomes from B16 melanoma cells. An antiserum raised against a Triton X-100 insoluble fraction of melanosomes recognized a 65-kDa protein in melanocytes from mice homozygous for the buff mutation, but not in their wild type counterparts. Further studies were conducted using a specific, second generation antiserum raised against the purified protein. The protein was also detected in melanocytes cultured from albino mice, but absent in cultured mouse cell lines not of melanocyte origin. Density gradient centrifugation of subcellular organelles and indirect immunofluorescent cell staining, indicated that the protein was associated with melanosomes and vesicles. The protein on intact organelles could be made soluble using sodium carbonate, and digested with proteases in the absence of detergent suggesting that it was a peripheral membrane protein localized on the cytosolic face of organelle membranes. Metabolic labelling of cells and N-glycosidase F digestion of cell extracts indicated that the protein was not N-glycosylated. Based on its intracellular localization and biochemical defects in the buff mouse, a potential role has been suggested for the 65-kDa protein in intracellular membrane trafficking

We describe a 10-day-old term infant who presented to the emergency room with an acute pustular eruption. Laboratory tests and clinical outcome confirmed the diagnosis of erythema toxicum neonatorum. A full septic workup was performed and all cultures were negative. Wright-stained smear of pustular contents showed a predominance of neutrophils with 10% eosinophils. The white blood cell count was 19,000/mm3 with 10% eosinophils. The eruption resolved spontaneously at 15 days of age leaving no sequelae. This is the first fully documented case of erythema toxicum in a term infant occurring as late as 10 days of age. When erythema toxicum presents in an atypical fashion, diagnostic tests are important to exclude other causes of pustular dermatoses of the neonate

We report 10 cases of neonatal erosions or ulcerations in giant congenital melanocytic nevi. Histopathologic examination, performed in eight cases, demonstrated benign findings. Clinical follow-up for an average of 3.8 years (range 2 weeks to 8 years) has not revealed the development of cutaneous melanoma. We conclude that erosions or ulcerations in giant melanocytic nevi in neonates are often benign and do not necessarily signify the presence of cutaneous melanoma