Loss-of-Function Mutations in SERPINB8 Linked to Exfoliative Ichthyosis with Impaired Mechanical Stability of Intercellular Adhesions
Loss-of-Function Mutations in SERPINB8 Linked to Exfoliative Ichthyosis with Impaired Mechanical Stability of Intercellular Adhesions
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DOI：
10.1016/j.ajhg.2016.06.004
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发表时间：
2016-08-04
影响因子：
9.8
通讯作者：
Blaydon, Diana C.
中科院分区：
文献类型：
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作者：
Pigors, Manuela;Sarig, Ofer;Blaydon, Diana C.
SERPINS包括丝氨酸蛋白酶抑制剂的大的和功能多样的家族。在这里，我们报告了三个不相关的家庭与SERPINB 8的功能丧失突变与常染色体隐性形式的剥脱性鱼鳞病。对来自一个突尼斯血缘家庭和一个以色列大家庭的受影响个体进行全外显子组测序，分别显示纯合移码突变c.947delA（p.Lys316Serfs*90）和无义突变c.850C>T（p.Arg284*）。这两个突变位于SERPINB 8的最后一个外显子中，因此预计不会导致mRNA的无义介导的衰变;尽管如此，预计这两个突变都会导致SERPINB 8的反应位点环的丢失，这对于形成SERPINB 8-蛋白酶复合物至关重要。使用桑格测序，纯合错义突变，c.2T>C（p.Met1？），在UAE的另外一个家族中鉴定了预测产生N-末端截短蛋白的突变。对来自变体p.Arg284* 纯合个体的皮肤活检的组织学分析显示，与对照相比，下表皮层中的角质形成细胞的粘连分离加上降低的SERPINB 8水平。在角质形成细胞中利用siRNA介导的SERPINB 8敲低的体外研究表明，在不存在蛋白质的情况下，存在细胞-细胞粘附缺陷，特别是当细胞受到机械应力时。此外，免疫印迹和免疫染色显示桥粒蛋白的上调。总之，我们报告了与剥脱性鱼鳞病相关的SERPINB 8突变，并提供了SERPINB 8有助于表皮细胞间粘附的机械稳定性的证据。
SERPINS comprise a large and functionally diverse family of serine protease inhibitors. Here, we report three unrelated families with lossof-function mutations in SERPINB8 in association with an autosomal-recessive form of exfoliative ichthyosis. Whole-exome sequencing of affected individuals from a consanguineous Tunisian family and a large Israeli family revealed a homozygous frameshift mutation, c.947delA (p.Lys316Serfs*90), and a nonsense mutation, c.850C>T (p.Arg284*), respectively. These two mutations are located in the last exon of SERPINB8 and, hence, would not be expected to lead to nonsense-mediated decay of the mRNA; nonetheless, both mutations are predicted to lead to loss of the reactive site loop of SERPINB8, which is crucial for forming the SERPINB8-protease complex. Using Sanger sequencing, a homozygous missense mutation, c.2T>C (p.Met1?), predicted to result in an N-terminal truncated protein, was identified in an additional family from UAE. Histological analysis of a skin biopsy from an individual homozygous for the variant p.Arg284* showed disadhesion of keratinocytes in the lower epidermal layers plus decreased SERPINB8 levels compared to control. In vitro studies utilizing siRNA-mediated knockdown of SERPINB8 in keratinocytes demonstrated that in the absence of the protein, there is a cell-cell adhesion defect, particularly when cells are subjected to mechanical stress. In addition, immunoblotting and immunostaining revealed an upregulation of desmosomal proteins. In conclusion, we report mutations in SERPINB8 that are associated with exfoliative ichthyosis and provide evidence that SERPINB8 contributes to the mechanical stability of intercellular adhesions in the epidermis.