Faculty Bibliography

Thymic stromal derived lymphopoietin receptor (TSLPR) is a novel receptor subunit that is related in sequence to the interleukin (IL)-2 receptor common gamma chain. TSLPR forms a heterodimeric complex with the IL-7 receptor alpha chain to form the receptor for thymic stromal derived lymphopoietin, a cytokine involved in B- and T-cell function. We have cloned the TSLP receptor from rat and find that the WSXWX motif commonly found in extracellular domains of cytokine receptors is conserved as a W(T/S)XV(T/A) motif among TSLP receptors from mouse, rat and human. As in the mouse, TSLP receptor is widely expressed in rats suggesting that TSLPR may have roles in signaling outside the hematopoietic system. A zooblot analysis revealed that TSLPR is expressed in all vertebrate species examined. The absence of TSLPR in Saccharomyces cerevisiae, Drosophila melanogaster and Caenorhabditis elegans genomes is similar to the expression of several other cytokine receptors that have been characterized thus far. We have also characterized the genomic structure of the murine Tslpr gene which shows that in addition to primary sequence homology, it shares a common genomic organization of coding exons with the murine IL-2 receptor common gamma chain (Il2rg). Use of an alternative splice acceptor site leads to two alternatively spliced transcript variants of murine TSLPR, both of which are functional receptors. Finally, using linkage analysis, we mapped the murine Tslpr gene to mouse chromosome 5 between the Ecm2 and Pxn genes.

Idiopathic congenital central hypoventilation syndrome (CCHS) is an unique disorder of respiratory control, occurring in association with Hirschsprung disease (HSCR), tumors of neural crest origin, and symptoms of autonomic nervous system dysfunction (ANSD). CCHS is thought to be genetic in origin based upon 1) affected sib pairs, 2) genetic analysis, and 3) identification of genetic mutations in both HSCR and CCHS patients. Because these mutations have been found in but a few cases of CCHS, exploration of other candidate genes has continued. Brain-derived neurotrophic factor (BDNF) represents a potential candidate gene to consider because of altered respiratory control in the BDNF knock-out mouse model and localization to the enteric nervous system in human tissue. The objective of this study was to determine the frequency of BDNF mutations among 19 children with CCHS (five with HSCR) compared to 40 unaffected unrelated controls. Using the known genomic DNA sequence for BDNF, polymerase chain reaction (PCR)-amplified genomic DNA was analyzed by standard sequencing methods. A discrete mutation was identified in one of 19 children with isolated CCHS and the unaffected father. Specifically, an isoleucine was substituted for a threonine or serine in the amino acid sequence. Absence of this mutation in 40 controls confirmed that this mutation was likely not a common polymorphism. These data further support a genetic basis for CCHS, though mutations of BDNF are not consistent in this disorder.

The human genome project is producing an enormous amount of sequence data, based on which single base changes between individuals can be identified. Unfortunately, computer tools that were adequate for sequence assembly are less than ideal for the characterization of polymorphism data [single nucleotide (snp) or insertion/deletion (indel)] and other sequence features, and their relationship to each other. We have developed viewGene as a flexible tool that takes input from a number of sequence formats and analysis programs (Genbank, FASTA, RepeatMasker, Cross match, BLAST, user-defined data) to construct a sequence reference scaffold that can be viewed through a simple graphical interface. polymorphisms generated from many sources can be added to this scaffold through the same sequence formats, with a variety of options to control what is displayed. Large amounts of polymorphism data can be organized so that patterns and haplotypes can be readily discerned. In our laboratory, viewGene has been used to view annotated genbank records, find nonrepetitive sequence fragments for polymorphism detection, and visualize similarity search results. Manipulation, cross-referencing, and haplotype viewing of snp data are essential for quality assessment and identification of variants associated with genetic disease, and viewGene provides all three of these important functions.

A genome-wide scan using 387 short tandem repeat markers was conducted for obesity among 618 black individuals from 202 families residing in a suburb of Chicago. Evidence for linkage was evaluated with BMI and percent body fat (PBF) using a variance component analysis approach. Suggestive evidence for linkage was found for BMI on chromosome 5 (logarithm of odds [LOD] score = 1.9) and PBF on chromosome 6 (LOD score = 2.7). One additional region on chromosome 3 was linked to these phenotypes at a lower level of significance (LOD score = 1.8 and 0.95 for BMI and PBF, respectively); the linked marker on this chromosome lies in the same region implicated as harboring obesity genes in a previous study of a white population. The replication of linkage evidence using different ethnic groups reinforces the potential significance of this latter candidate region.

This unit opens with a comparison of radiation hybrid and somatic cell hybrid analyses. Definitions, assumptions, and a mathematical model for radiation hybrid analysis are presented. In addition, parametric and nonparametric methods of data analysis are presented.

The study of vertebrate pigmentary anomalies has greatly improved our understanding of melanocyte biology. One such disorder, Waardenburg syndrome (WS), is a mendelian trait characterized by hypopigmentation and sensorineural deafness. It is commonly subdivided into four types (WS1-4), defined by the presence or absence of additional symptoms. WS type 4 (WS4), or Shah-Waardenburg syndrome, is also known as Hirschsprung disease Type II (HSCR II) and is characterized by an absence of epidermal melanocytes and enteric ganglia. Mutations in the genes encoding the endothelin type-B receptor (EDNRB) and its physiological ligand endothelin 3 (EDN3) are now known to account for the majority of HSCR II patients. Null mutations in the mouse genes Ednrb and Edn3 have identified a key role for this pathway in the normal development of melanocytes and other neural crest-derived lineages. The pleiotropic effects of genes in this pathway, on melanocyte and enteric neuron development, have been clarified by the embryologic identification of their common neural crest (NC) ancestry. EDNRB and EDN3 are transiently expressed in crest-derived melanoblast and neuroblast precursors, and in the surrounding mesenchymal cells, respectively. The influence of EDNRB-mediated signaling on the emigration, migration, proliferation, and differentiation of melanocyte and enteric neuron precursors, in vivo and in vitro has recently been the subject of great scrutiny. A major emergent theme is that EDN3-induced signaling prevents the premature differentiation of melanocyte and enteric nervous system precursors and is essential between 10 and 12.5 days post-coitum. We review the present understanding of pigment cell development in the context of EDNRB/EDN3--a receptor-mediated pathway with pleiotropic effects.

Satin (sa) homozygous mice have a silky coat with high sheen arising from structurally abnormal medulla cells and defects in differentiation of the hair shaft. We demonstrate that the winged helix/forkhead transcription factor, Foxq1 (Forkhead box, subclass q, member 1) is mutant in sa mice. An intragenic deletion was identified in the radiation-induced satin mutant of the SB/Le inbred strain; a second allele, identified by an N-ethyl-N-nitrosourea (ENU) mutagenesis screen, has a missense mutation in the conserved winged helix DNA-binding domain. Homozygous mutants of the two alleles are indistinguishable. We show that Foxq1 is expressed during embryogenesis and exhibits a tissue-restricted expression pattern in adult tissues. The hair defects appear to be restricted to the inner structures of the hair; consequently, Foxq1 has a unique and distinct function involved in differentiation and development of the hair shaft. Despite an otherwise healthy appearance, satin mice have been reported to exhibit suppressed NK-cell function and alloimmune cytotoxic T-cell function. We show instead that the immune defects are attributable to genetic background differences.