Juriloff Diana M, Harris Muriel J, Dewell Sarah L
Department of Medical Genetics, University of British Columbia, Vancouver, British ColumbiaV6T 1Z3, Canada.
Birth Defects Res A Clin Mol Teratol. 2004 Aug;70(8):509-18. doi: 10.1002/bdra.20041.
Nonsyndromic cleft lip with or without cleft palate, CL(P), is a common human birth defect with a complex unknown genetic cause. The mouse model is the "A/-" strains. Our previous studies mapped two loci: clf1 on Chr11 and clf2 on Chr13--with a strong genetic maternal effect on the level of risk. Here we test the hypothesis that CL(P) is digenic and identify candidate genes for clf1 and clf2.
We observed E14 CL(P) frequencies in backcross (BC1) embryos from a new cross of A/WySn to AXB-4/Pgn and from test crosses of three new "congenic RI" lines. Using new polymorphic markers from genes and our mapping panels of segregants and RI strains, we identified the candidate genes for clf1 and clf2. We sequenced the coding region of Ptch in A/WySn cDNA.
Seventy new BC1 CL(P) segregants (4%) were obtained, as predicted. All three new congenic RI lines homozygous for both clf1 and clf2 had A/WySn-level CL(P) frequencies (10-30%) in test crosses. The clf1 region contains 10 known genes (Arf2, Cdc27, Crhr1, Gosr2, Itgb3, Mapt, Myl4, Nsf, Wnt3, and Wnt9b). The clf2 region contains 17 known genes with human orthologs. Both regions contain additional potential genes. No causal mutation in Ptch coding sequence was found.
In A-strain mice, nonsyndromic CL(P) is digenic, suggesting that nonsyndromic human CL(P) may also be digenic. The orthologous human genes are on 17q (clf1) and 9q, 8q and 5p (clf2), and good candidate genes are WNT3 or WNT9B (17q), and PTCH (9q) or MTRR (5p).
非综合征性唇裂伴或不伴腭裂（CL(P)）是一种常见的人类出生缺陷，其遗传病因复杂且未知。小鼠模型为“A/-”品系。我们之前的研究定位了两个基因座：位于11号染色体上的clf1和位于13号染色体上的clf2，且遗传母系效应在风险水平上具有重要影响。在此，我们检验CL(P)是双基因遗传的假说，并鉴定clf1和clf2的候选基因。
我们观察了来自A/WySn与AXB-4/Pgn新杂交组合的回交（BC1）胚胎以及三个新的“同源重组近交系”品系测交后代中E14期CL(P)的频率。利用来自基因的新多态性标记以及我们的分离群体和重组近交系品系的定位面板，我们鉴定了clf1和clf2的候选基因。我们对A/WySn cDNA中Ptch的编码区进行了测序。
如预期那样，获得了70个新的BC1 CL(P)分离个体（4%）。所有三个同时对clf1和clf2纯合的新同源重组近交系在测交中的CL(P)频率均达到A/WySn水平（10 - 30%）。clf1区域包含10个已知基因（Arf2、Cdc27、Crhr1、Gosr2、Itgb3、Mapt、Myl4、Nsf、Wnt3和Wnt9b）。clf2区域包含17个具有人类同源基因的已知基因。两个区域都包含其他潜在基因。在Ptch编码序列中未发现致病突变。
在A品系小鼠中，非综合征性CL(P)是双基因遗传的，这表明人类非综合征性CL(P)也可能是双基因遗传的。人类同源基因位于17号染色体（clf1）以及9号染色体、8号染色体和5号染色体（clf2）上，良好的候选基因是WNT3或WNT9B（17号染色体），以及PTCH（9号染色体）或MTRR（5号染色体）。
