Department of Pediatrics, Peking University First Hospital, Beijing, China.
Laboratory of Electron Microscopy, Ultrastructural Pathology Center, Peking University First Hospital, Beijing, China.
Mol Genet Genomic Med. 2021 Jul;9(7):e1704. doi: 10.1002/mgg3.1704. Epub 2021 May 13.
Both Pierson syndrome (PS) and isolated nephrotic syndrome can be caused by LAMB2 biallelic pathogenic variants. Only 15 causative splicing variants in the LAMB2 gene have been reported. However, the pathogenicity of most of these variants has not been verified, which may lead to incorrect interpretation of the functional consequence of these variants.
Using high-throughput DNA sequencing and Sanger sequencing, we detected variants in a female with clinically suspected PS. A minigene splicing assay was performed to assess the effect of LAMB2 intron 20 c.2885-9C>A on RNA splicing. We also performed the immunohistochemical analysis of laminin beta-2 in kidney tissues.
Two novel LAMB2 heteroallelic variants were found: a paternally inherited variant c.2885-9C>A in intron 20 and a maternally inherited variant c. 3658C>T (p. (Gln1220Ter)). In vitro minigene assay showed that the variant c.2885-9C>A caused erroneous integration of a 7 bp sequence into intron 20. Immunohistochemical analysis revealed the absence of glomerular expression of laminin beta-2, the protein encoded by LAMB2.
We demonstrated the impact of a novel LAMB2 intronic variant on RNA splicing using the minigene assay firstly. Our results extend the mutational spectrum of LAMB2.
Pierson 综合征（PS）和单纯性肾病综合征均可由 LAMB2 双等位致病性变异引起。LAMB2 基因中仅报道了 15 个致病剪接变异体。然而，这些变异体中的大多数致病性尚未得到验证，这可能导致对这些变异体功能后果的错误解释。
使用高通量 DNA 测序和 Sanger 测序，我们检测了一名临床疑似 PS 女性的变异体。进行了 minigene 剪接分析，以评估 LAMB2 内含子 20 c.2885-9C>A 对 RNA 剪接的影响。我们还对肾脏组织中的层粘连蛋白β-2 进行了免疫组织化学分析。
发现了两种新的 LAMB2 异等位变异体：父系遗传的变异 c.2885-9C>A 位于内含子 20 中，以及母系遗传的变异 c.3658C>T（p.（Gln1220Ter））。体外 minigene 分析表明，变异 c.2885-9C>A 导致 7 bp 序列错误地整合到内含子 20 中。免疫组织化学分析显示，层粘连蛋白β-2（由 LAMB2 编码的蛋白质）在肾小球中的表达缺失。
我们首次通过 minigene 分析证明了新型 LAMB2 内含子变异对 RNA 剪接的影响。我们的结果扩展了 LAMB2 的突变谱。
