背景:常染色体隐性遗传皮肤松弛2A型(ARCL2A;OMIM:219200)的特征是神经营养,发育和孕激素弹性皮肤异常。它是由ATPase的双等位基因变异引起的,H+转运V0亚基A2(ATP6V0A2;OMIM:611716)位于染色体12q24.31上。常染色体隐性遗传皮肤松弛3A型(ARCL3A;OMIM:219150)是另一种以身材矮小为特征的亚临床型,眼科异常和早衰样外观。ARCL3A是由位于染色体10q24.1的醛脱氢酶18家族成员A1(ALDH18A1;OMIM:138250)基因的功能改变丢失引起的。
方法:全外显子组测序(WES),并进行Sanger测序进行分子诊断。进行3D蛋白质建模以研究变体对蛋白质结构的有害作用。
结果:在这项研究中,对两个家庭进行了临床和分子诊断,ED-01和DWF-41,显示了ARCL2A和ARCL3A的标志性特征,分别。ED-01家族中的三个受影响个体(IV-4,IV-5和V-3)显示皮肤松弛,向下倾斜的睑裂,腹部皱纹过多,手和脚,躯干上有突出的静脉.同时,DWF-41家族(V-2和V-3)中的受影响个体具有早衰性皮肤,身材矮小,形态学,低肌肉张力,癫痫,脊柱前凸,脊柱侧弯,青春期和内生殖器延迟。WES在索引患者(ED-01:IV-4)中鉴定出ATP6V0A2外显子16中的新纯合缺失(NM_012463.3:c.1977_1980del;p。[Val660LeufsTer23]),而在DWF-41中,一个新的纯合错义变体(NM_0013234131313.1:c.1867)在Asp所有可用家庭成员的Sanger验证证实了每个家庭中遗传的常染色体隐性模式。三维计算机蛋白质建模表明鉴定的变体的有害影响。此外,根据美国医学遗传学学会2015年指南,这些变异体被分为1类或"致病性".筛选种族匹配的健康对照(n=200条染色体),排除了一般人群中这些变异的存在。
结论:据我们所知,这是巴基斯坦人口Pakhtun种族中ATP6V0A2和ALDH18A1变异的第一份报告。该研究证实,WES可用作皮肤松弛症患者的一线诊断测试,并为人口筛查和婚前检查提供基础,以减轻后代的疾病负担。
Autosomal recessive cutis laxa type 2A (ARCL2A; OMIM: 219200) is characterized by neurovegetative, developmental and progeroid elastic skin anomalies. It is caused by biallelic variation in ATPase, H+ transporting V0 subunit A2 (ATP6V0A2; OMIM: 611716) located on chromosome 12q24.31. Autosomal recessive cutis laxa type 3A (ARCL3A; OMIM: 219150) is another subclinical type characterized by short stature, ophthalmological abnormalities and a progeria-like appearance. The ARCL3A is caused by loss of function alterations in the aldehyde dehydrogenase 18 family member A1 (
ALDH18A1; OMIM: 138250) gene located at chromosome 10q24.1.
Whole-exome sequencing (WES), and Sanger sequencing were performed for molecular diagnosis. 3D protein modeling was performed to investigate the deleterious effect of the variant on protein structure.
In this study, clinical and molecular diagnosis were performed for two families, ED-01 and DWF-41, which displayed hallmark features of ARCL2A and ARCL3A, respectively. Three affected individuals in the ED-01 family (IV-4, IV-5 and V-3) displayed sagging loose skin, down-slanting palpebral fissures, excessive wrinkles on the abdomen, hands and feet, and prominent veins on the trunk. Meanwhile the affected individuals in the DWF-41 family (V-2 and V-3) had progeroid skin, short stature, dysmorphology, low muscle tone, epilepsy, lordosis, scoliosis, delayed puberty and internal genitalia. WES in the index patient (ED-01: IV-4) identified a novel homozygous deletion (NM_012463.3: c.1977_1980del; p.[Val660LeufsTer23]) in exon 16 of the ATP6V0A2 while in DWF-41 a novel homozygous missense variant (NM_001323413.1:c.1867G>A; p.[Asp623Asn]) in exon 15 of the
ALDH18A1 was identified. Sanger validation in all available family members confirmed the autosomal recessive modes of inheritances in each family. Three dimensional in-silico protein modeling suggested deleterious impact of the identified variants. Furthermore, these variants were assigned class 1 or \"pathogenic\" as per guidelines of American College of Medical Genetics 2015. Screening of ethnically matched healthy controls (n = 200 chromosomes), excluded the presence of these variations in general population.
To the best of our knowledge, this is the first report of ATP6V0A2 and
ALDH18A1 variations in the Pakhtun ethnicity of Pakistani population. The study confirms that WES can be used as a first-line diagnostic test in patients with cutis laxa, and provides basis for population screening and premarital testing to reduce the diseases burden in future generations.