RET Mutational Spectrum in Hirschsprung Disease: Evaluation of 601 Chinese Patients

Rare (RVs) and common variants of the RET gene contribute to Hirschsprung disease (HSCR; congenital aganglionosis). While RET common variants are strongly associated with the commonest manifestation of the disease (males; short-segment aganglionosis; sporadic), rare coding sequence (CDS) variants are more frequently found in the lesser common and more severe forms of the disease (females; long/total colonic aganglionosis; familial). Here we present the screening for RVs in the RET CDS and intron/exon boundaries of 601 Chinese HSCR patients, the largest number of patients ever reported. We identified 61 different heterozygous RVs (50 novel) distributed among 100 patients (16.64%). Those include 14 silent, 29 missense, 5 nonsense, 4 frame-shifts, and one in-frame amino-acid deletion in the CDS, two splice-site deletions, 4 nucleotide substitutions and a 22-bp deletion in the intron/exon boundaries and 1 single-nucleotide substitution in the 5′ untranslated region. Exonic variants were mainly clustered in RET the extracellular domain. RET RVs were more frequent among patients with the most severe phenotype (24% vs. 15% in short-HSCR). Phasing RVs with the RET HSCR-associated haplotype suggests that RVs do not underlie the undisputable association of RET common variants with HSCR. None of the variants were found in 250 Chinese controls.

RET基因的稀有变异（rare variants, RVs）与常见变异均参与先天性巨结肠（Hirschsprung disease, HSCR，又称先天性无神经节症congenital aganglionosis）的发病过程。其中RET常见变异与该病最常见的临床表型强相关，即男性患者、短段型无神经节症、散发性病例；而稀有编码序列（coding sequence, CDS）变异则更常出现在发病率较低但病情更为严重的表型中，包括女性患者、长段型/全结肠型无神经节症以及家族性病例。本研究对601例中国HSCR患者的RET基因CDS区及内含子/外显子边界区域的稀有变异进行了筛查，该样本规模为迄今已报道的最大病例队列。本研究在100例患者中检出61种不同的杂合型稀有变异（其中50种为新发现变异），总体检出率为16.64%。上述变异涵盖以下类型：CDS区内的14种沉默变异、29种错义变异、5种无义变异、4种移码变异以及1种框内氨基酸缺失；内含子/外显子边界区域的2种剪接位点变异、4种核苷酸替换以及1段22bp缺失；以及5'非翻译区（5' untranslated region）内的1处单核苷酸替换。外显子变异主要聚集于RET基因的胞外结构域。在病情最严重的HSCR患者中，RET稀有变异的检出率显著更高（24% vs. 短段型HSCR患者的15%）。对稀有变异与RET基因HSCR相关单倍型的单体型分型分析显示，稀有变异并非RET常见变异与HSCR明确关联的遗传学基础。250例中国对照人群中未检出任何上述变异。