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Keywords:

  • Hirschsprung disease;
  • Waardenburg syndrome;
  • Endothelin;
  • Hypopigmentation;
  • Melanocyte;
  • Neural crest

Abstract

  1. Top of page
  2. Abstract

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.

Abbreviations
dpc

days post-coitum

EDN3

endothelin 3

EDNRB

endothelin type-B receptor

ENS

enteric nervous system

GPCR

G-protein coupled receptor

HSCR

Hirschsprung disease

KIT

steel factor receptor

MGF

mast cell growth factor

MITF

micropthalmia transcription factor

NC

neural crest

NT

neural tube

PAX3

paired box gene 3

RTK

receptor tyrosine kinase

SOX10

sry-box gene 10

WS

Waardenburg syndrome