Mrad Ridha, Dorboz Imen, Ben Jemaa Lamia, Maazoul Faouzi, Trabelsi Madiha, Chaabouni Meriem, Mlaiki Brahim, Miladi Nakjoua, Hentati Faycel, Chaabouni Habiba
Department of Human Genetics Charles, Nicolle Hospital, Tunis, Tunisia.
Tunis Med. 2006 Aug;84(8):465-9.
In this study we examined the deletion of SMN and NAIP genes in 60 Tunisian families. There were 35 patients with type I SMA. 18 with type II SMA. 6 with type III SMA and I with type IV SMA. The age of onset was before 6 months for type I, between 6 months and 2 years for type II, between 2 years and 17 years for type III and 30 years for type IV. Exon 7 of SMNI gene was homozygously deleted in 95% (57/60) of SMA patients. There was a higher frequency of homozygous absence of SMN1 in type I and type II (100% and 94% respectively) than in type III (66,7%). SMN1 exon 8 was undetectable in 88% (53/60) of patients. The case type II patient with homozygous deletion of SMNI exon 7 and not exon 8 was tested for the presence of a hybrid SMN gene. This patient showed in the second PCR a SMN1 exon 8 product by restriction site assay indicating that a gene conversion event had occurred. All parents' individuals retained one copy of their SMN1 gene. Exon 5 of NAIP gene was homozygously deleted in 58% (35/60) of patients (77% in type I (27/35), 27,7% in type II (5/18), 50% (3/6) in type III. No patient had a deletion in NAIP gene without a deletion in the SMN1 gene. Homozygous deletion of NAIP exon 5 was detected in 1 parent. Our results show that the incidence of NAIP deletion is higher in the more severe SMA cases.
在本研究中，我们检测了60个突尼斯家庭中SMN和NAIP基因的缺失情况。其中有35例I型脊髓性肌萎缩症（SMA）患者，18例II型SMA患者，6例III型SMA患者和1例IV型SMA患者。发病年龄I型在6个月之前，II型在6个月至2岁之间，III型在2岁至17岁之间，IV型为30岁。95%（57/60）的SMA患者中SMNI基因的外显子7纯合缺失。I型和II型中SMN1纯合缺失的频率更高（分别为100%和94%），高于III型（66.7%）。88%（53/60）的患者中未检测到SMN1外显子8。对1例II型患者进行检测，其SMNI外显子7纯合缺失但外显子8未缺失，检测其是否存在杂交SMN基因。该患者在第二次聚合酶链反应（PCR）中通过限制性酶切位点分析显示有SMN1外显子8产物，表明发生了基因转换事件。所有父母个体均保留其SMN1基因的一个拷贝。58%（35/60）的患者中NAIP基因的外显子5纯合缺失（I型中为77%（27/35），II型中为27.7%（5/18），III型中为50%（3/6））。没有患者NAIP基因缺失而SMN1基因未缺失。在1名父母中检测到NAIP外显子5纯合缺失。我们的结果表明，在病情更严重的SMA病例中，NAIP缺失的发生率更高。
