两个斑驳病家系KIT基因突变研究

Identification of novel KIT gene mutations in two Chinese families with piebaldism

目的对2个斑驳病家系进行致病基因突变分析，为患者及其家系成员提供遗传咨询和生育指导。方法分别采集家系1两例患者（先证者及其父亲）、家系2先证者及3名表型正常家系成员的外周血，提取外周血DNA和RNA。应用PCR、逆转录PCR及测序等技术，从基因组水平和表达水平对此两家系先证者和患者进行KIT基因诊断，并初步探讨检测到的突变对KIT基因功能的影响。结果家系1中两例患者KIT基因均存在IVSl2＋2_＋7delinsACATCTTTA的杂合突变，该突变在cDNA水平导致KIT基因c．1765-1779del突变，在氨基酸水平导致p．Gly592Ala／del：E12突变，使得KIT基因剪切位点发生改变，即其中一条cDNA第12外显子被跨越、未转录。家系2中先证者KIT基因存在c．2401A〉C突变，3位表型正常的家系成员未见该突变。结论确诊了两个斑驳病家系的致病原因。家系1患者KIT基因均存在IVSl2＋2_＋7delinsAcATcTTTA的杂合突变，该突变为人类基因突变数据库未记载的、新的剪切突变；家系2先证者KIT基因存在c．2401A〉C突变，结合3位表型正常的家系成员KIT基因未见c．240LA〉C突变，推测该突变为先证者患斑驳病的致病突变可能性大。为此两家系进行遗传咨询和产前诊断提供了理论依据。

Objective To screen for potential mutations of KIT gene for two Chinese families affected with piebaldism in order to facilitate genetic counseling and assisted reproduction. Methods Peripheral blood samples were collected from 2 patients of family 1 and the proband and 3 unaffected members of family 2 for the extraction of DNA and RNA. PCR-sequencing and reverse transcription-PCR-sequencing were used to screen KIT mutations. Results All of the patients from family 1 were found to carry heterozygous IVS12 ＋2_＋ 7delinsACATCTTTA, a splicing mutation undocumented in the human gene mutation data base （HGMD） database. This mutation has resulted in c. 1765-1779del in cDNA and p. Gly592Ala/del： El2, which has led to skipping of exon 12 and no expression of cDNA. The proband from family 2 has carried a heterozygous c. 2401A〉C mutation in KIT gene. The same mutation was not found in unaffected members. Conclusion We have attained definite diagnosis for both families, which has facilitated genetic counseling and assisted reproduction for our patients and their family members.