GENETIC INTERACTIONS COORDINATING PIEBALD SPOTTING

在花斑小鼠中观察到的黑色和白色斑点图案结果 由于内皮素突变导致神经嵴发育异常 受体B（EDNRB）。色素斑的严重程度和分布 在两个携带s突变的近交系中有很大的不同 （Mayer/s和C3H s/s）。我们假设，额外的基因可能是 负责协调观察到的图案差异。 这两个品系回交后代的数量遗传分析 鉴定了位于染色体2、5、8和10上的四种遗传修饰剂。 10号染色体上的修饰符使背侧斑点增加2倍以上 腹侧点样法（19.7% vs 9.1%，p < 0.0001），表明 修饰符对颜料图案化具有空间或时间影响。分析 的映射数据暗示钢（肥大细胞生长因子）作为候选人 这个基因座。cDNA分离物的序列比较没有 指示编码区中的任何差异，然而， 用北方杂交法检测成年组织中稳态mRNA水平 分析。Steel基因的基因组结构比较 证明12/12的限制性内切酶显示大小差异 然而，在两个未连接的DNA片段中没有观察到差异。 基因，EDNRB和内皮素3。这些结果表明， 在迈耶品系的s小鼠中观察到的斑点是由于一种突变， 改变了Steel的表达模式。我们已经通过 使用Mayer品系和Steel无效小鼠之间的杂交。一致 根据我们的假设，Steel上的Mayer等位基因不能与Steel互补， 无效突变并导致背部斑点增加。未来的研究 利用胚胎重建实验和表达模式研究 还将探索以确定分子改变， 每个修饰位点的相互作用。

The black and white spotting pattern observed in piebald (s) mice results from abnormal neural crest development due to a mutation in endothelin receptor B (EDNRB). The severity and distribution of the pigment patterns are vastly different in two inbred strains carrying the s mutation (Mayers/s and C3H s/s). We hypothesized that additional genes may be responsible for coordinating the differences in patterning observed. Quantitative genetic analysis of backcross progeny from these two strains identified four genetic modifiers located on Chromosomes 2, 5, 8 and 10. The modifier on Chromosome 10 increases the dorsal spotting 2-fold more than ventral spotting (19.7% vs 9.1%, p < 0.0001), suggesting this modifier has spatial or temporal affects on pigment patterning. Analysis of mapping data implicates Steel (mast cell growth factor) as a candidate gene for this locus. Sequence comparison of cDNA isolates did not indicate any differences in the coding region, however differences in the level of steady state mRNA in adult tissues was observed by Northern blot analyses. Comparison of the genomic structure of the Steel gene demonstrated 12/12 restriction enzymes showing differences in the size of DNA fragments, however no differences were observed in two un-linked genes, EDNRB and endothelin 3. These results suggest the increased dorsal spotting observed in the Mayer strain of s mice is due to a mutation that alters the Steel expression pattern.We have tested this hypothesis by using crosses between the Mayer strain and Steel null mice. Consistent with our hypothesis, the Mayer allele at Steel cannot complement a Steel null mutation and results in increased dorsal spotting. Future studies using embryonic reconstitution experiments and expression pattern studies will also be explored to determine the molecular alterations and interactions at each modifier locus.