Fukami Maki, Dateki Sumito, Kato Fumiko, Hasegawa Yukihiro, Mochizuki Hiroshi, Horikawa Reiko, Ogata Tsutomu
Department of Endocrinology and Metabolism, National Research Institute for Child Health and Development, 2-10-1 Ohkura, Setagaya, Tokyo, 157-8535, Japan.
Department of Pediatrics, Nagasaki University School of Medicine, Nagasaki, Japan.
J Hum Genet. 2008;53(5):454-459. doi: 10.1007/s10038-008-0269-z. Epub 2008 Mar 6.
Although short-stature homeobox-containing gene (SHOX ) haploinsufficiency is responsible for Léri-Weill dyschondrosteosis (LWD), the molecular defect has not been identified in approximately 20% of Japanese LWD patients. Furthermore, although high prevalence of microdeletions affecting SHOX is primarily ascribed to the presence of repeat sequences such as Alu elements around SHOX, it remains to be determined whether microdeletions are actually mediated by repeat sequences. We performed multiple ligation probe amplification (MLPA) assay in six Japanese LWD patients with apparently normal SHOX, followed by fluorescent in situ hybridization (FISH) analysis and sequencing for polymerase chain reaction (PCR) products encompassing the deletion junctions in patients with abnormal MLPA patterns. Consequently, heterozygous intragenic deletions were identified in three cases, i.e., a 5,906-bp deletion involving exons 4-5 in case 1, a 5,594-bp deletion involving exons 4-6a in case 2, and a 50,199-bp deletion involving exons 4-6b in case 3. The deletion breakpoints of cases 1 and 2 were present in nonrepeat sequences, whereas those of case 3 resided within Alu elements. The results suggest that cryptic SHOX intragenic deletions account for a small fraction of LWD and that microdeletions affecting SHOX can be generated by repeat-sequence-mediated aberrant recombinations and by nonhomologous end joining.
虽然含矮小同源框基因（SHOX）单倍体不足是Léri-Weill软骨发育不全症（LWD）的病因，但在约20%的日本LWD患者中尚未发现分子缺陷。此外，虽然影响SHOX的微缺失高发生率主要归因于SHOX周围存在如Alu元件等重复序列，但微缺失是否实际由重复序列介导仍有待确定。我们对6例SHOX明显正常的日本LWD患者进行了多重连接探针扩增（MLPA）检测，随后对MLPA模式异常患者的包含缺失连接点的聚合酶链反应（PCR）产物进行荧光原位杂交（FISH）分析和测序。结果，在3例患者中鉴定出杂合性基因内缺失，即病例1中涉及外显子4 - 5的5906 bp缺失，病例2中涉及外显子4 - 6a的5594 bp缺失，病例3中涉及外显子4 - 6b的50199 bp缺失。病例1和病例2的缺失断点存在于非重复序列中，而病例3的缺失断点位于Alu元件内。结果表明，隐匿性SHOX基因内缺失占LWD的一小部分，且影响SHOX的微缺失可由重复序列介导的异常重组和非同源末端连接产生。
