Lu Yuan, Boswell Mikki, Boswell William, Kneitz Susanne, Hausmann Michael, Klotz Barbara, Regneri Janine, Savage Markita, Amores Angel, Postlethwait John, Warren Wesley, Schartl Manfred, Walter Ronald
The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas.
Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany.
Mol Carcinog. 2017 Aug;56(8):1935-1944. doi: 10.1002/mc.22651. Epub 2017 Apr 13.
Development of spontaneous melanoma in Xiphophorus interspecies backcross hybrid progeny, (X. hellerii × [X. maculatus Jp 163 A × X. hellerii]) is due to Mendelian segregation of a oncogene (xmrk) and a molecularly uncharacterized locus, called R(Diff), on LG5. R(Diff) is thought to suppresses the activity of xmrk in healthy X. maculatus Jp 163 A parental species that rarely develop melanoma. To better understand the molecular genetics of R(Diff), we utilized RNA-Seq to study allele-specific gene expression of spontaneous melanoma tumors and corresponding normal skin samples derived from 15 first generation backcross (BC ) hybrids and 13 fifth generation (BC ) hybrids. Allele-specific expression was determined for all genes and assigned to parental allele inheritance for each backcross hybrid individual. Results showed that genes residing in a 5.81 Mbp region on LG5 were exclusively expressed from the X. hellerii alleles in tumor-bearing BC hybrids. This observation indicates this region is consistently homozygous for X. hellerii alleles in tumor bearing animals, and therefore defines this region to be the R(Diff) locus. The R(Diff) locus harbors 164 gene models and includes the previously characterized R(Diff) candidate, cdkn2x. Twenty-one genes in the R(Diff) region show differential expression in the tumor samples compared to normal skin tissue. These results further characterize the R(Diff) locus and suggest tumor suppression may require a multigenic region rather than a single gene variant. Differences in gene expression between tumor and normal skin tissue in this region may indicate interactions among several genes are required for backcross hybrid melanoma development.
剑尾鱼属种间回交杂种后代（X. hellerii × [X. maculatus Jp 163 A × X. hellerii]）中自发性黑色素瘤的发生是由于一个癌基因（xmrk）和位于LG5上一个分子特征未明的位点R(Diff)的孟德尔分离。R(Diff)被认为在很少发生黑色素瘤的健康X. maculatus Jp 163 A亲本物种中抑制xmrk的活性。为了更好地理解R(Diff)的分子遗传学，我们利用RNA测序研究了来自15个第一代回交（BC1）杂种和13个第五代（BC5）杂种的自发性黑色素瘤肿瘤及相应正常皮肤样本的等位基因特异性基因表达。确定了所有基因的等位基因特异性表达，并为每个回交杂种个体分配了亲本等位基因遗传情况。结果显示，LG5上一个5.81 Mbp区域内的基因在携带肿瘤的BC杂种中仅从X. hellerii等位基因表达。这一观察结果表明，在携带肿瘤的动物中，该区域对于X. hellerii等位基因始终是纯合的，因此将该区域定义为R(Diff)位点。R(Diff)位点包含164个基因模型，包括先前鉴定的R(Diff)候选基因cdkn2x。与正常皮肤组织相比，R(Diff)区域中的21个基因在肿瘤样本中表现出差异表达。这些结果进一步描述了R(Diff)位点的特征，并表明肿瘤抑制可能需要一个多基因区域而非单个基因变体。该区域肿瘤组织与正常皮肤组织之间的基因表达差异可能表明，回交杂种黑色素瘤的发生需要几个基因之间的相互作用。
