Abstract: PO1342
Pathogenicity Assessment of Non-Glycine Missense Variants in COL4A5 Collagenous Domain
Session Information
- Genetic Diseases of the Kidneys: Non-Cystic - II
November 04, 2021 | Location: On-Demand, Virtual Only
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1002 Genetic Diseases of the Kidneys: Non-Cystic
Authors
- Aoto, Yuya, Kobe Daigaku, Kobe, Hyogo, Japan
- Horinouchi, Tomoko, Kobe Daigaku, Kobe, Hyogo, Japan
- Yamamura, Tomohiko, Kobe Daigaku, Kobe, Hyogo, Japan
- Nagano, China, Kobe Daigaku, Kobe, Hyogo, Japan
- Kondo, Atsushi, Kobe Daigaku, Kobe, Hyogo, Japan
- Nagai, Sadayuki, Kobe Daigaku, Kobe, Hyogo, Japan
- Sakakibara, Nana, Kobe Daigaku, Kobe, Hyogo, Japan
- Iijima, Kazumoto, Hyogo Kenritsu Kodomo Byoin, Kobe, Hyogo, Japan
- Nozu, Kandai, Kobe Daigaku, Kobe, Hyogo, Japan
Background
COL4A5, which encodes type IV collagen α5 chain, is a causative gene of X-linked Alport Syndrome (XLAS). In triple-helical domain on collagen protein (collagenous domain), the amino acid strictly repeats glycine (Gly) in every third position, (Gly-Xaa-Yaa)n, and these Gly contribute to the stability of triple-helical structure. Because of this, within collagenous domain, most Gly missense variants are pathogenic, and most reported missense variants substitutes amino acids from Gly. However, several pathogenic missense variants other than Gly (non-Gly missense variants) have been reported and the mechanisms of disease onset by these variants are not clear until now. The aim of this current study is to investigate the pathogenicity of non-Gly missense variants in COL4A5 collagenous domain.
Methods
We extracted 18 variants, 13 from the Human Gene Mutation Database and 5 identified in our cohort. Firstly, we conducted a functional splicing assay using a hybrid minigene analysis method to examine the existence of aberrant splicing. Then, variants not causing aberrant splicing were investigated for the characteristics including bioinformatics analysis.
Results
Seven out of eighteen (38.9%) non-Gly variants caused aberrant splicing and then, exhibited XLAS. In addition, three of these variants resulted in both exon skipping and normal splicing, and these three patients showed milder phenotypes. Five of the 12 variants not causing aberrant splicing were missense variants substituted from Proline (Pro) located at Yaa of (Gly-Xaa-Yaa)n. Pro at this position is hydroxylated and results in the stabilization of the triple-helix structure. Bioinformatics analysis showed that Pro missense variants decrease the structural flexibility. Two of the remaining variants were located in the interrupted domains, which are outside of the (Gly-Xaa-Yaa)n repeat. These interrupted domains are related to the flexibility of the collagen molecule or related to network in the basement membrane. Therefore, these 2 variants were considered to influence the triple-helix structure.
Conclusion
We revealed the new mechanisms showing pathogenicity of non-Gly missense variants in COL4A5 collagenous domain.
Funding
- Government Support – Non-U.S.