Identification and functional analysis of a SLC33A1: c.339T>G (p.Ser113Arg) variant in the original SPG42 family.
Using whole-exome sequencing, we surveyed all the potential pathogenic variants in an SPG42 family and found five SNPs and four indels that are shared by two patients and lie in the mapped region. Two variants, SLC33A1 p.Ser113Arg and VEPH1 p.Gln433His, cosegregated with the disease. However, VEPH1 p.Gln433His was predicted to be tolerated, thus leaving SLC33A1 p.Ser113Arg as the most plausible causal variant in this family. We found that the phosphorylated SMAD1/5/8 (P-SMAD1/5/8) and BMP receptor type 1A (BMPR1A) were substantially upregulated in fibroblasts derived from an SPG42 individual. Slc33a1 knockdown zebrafish, which exhibited defects in morphology and axon outgrowth, also showed a significant elevation in the level of P-smad1/5/8. While the phenotypes in slc33a1 knockdown zebrafish could be rescued by human wild-type SLC33A1 mRNA, this rescuing effect was diminished by coinjected mutant mRNA encoding p.Ser113Arg, indicating that p.Ser113Arg variant acts in a dominant-negative manner. Importantly, pharmacological blockade of BMPR1 activity by dorsomorphin could efficiently rescue the phenotypic defects in slc33a1 knockdown zebrafish. These results indicate that SLC33A1 can negatively regulate BMP signaling.
The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Genetics, Shandong University School of Medicine, Jinan, Shandong, 250012, China.
Fei
F
Mao
Zhaohui
Z
Li
Baoyue
B
Zhao
Pengfei
P
Lin
Pingting
P
Liu
Meng
M
Zhai
Qiji
Q
Liu
Changshun
C
Shao
Wenjie
W
Sun
Yaoqin
Y
Gong
D019943:Amino Acid Substitution; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D056726:Genetic Association Studies; D006801:Humans; D054643:INDEL Mutation; D026901:Membrane Transport Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D015398:Signal Transduction; D015419:Spastic Paraplegia, Hereditary / Q000235:genetics*; D015027:Zebrafish
D019485:Bone Morphogenetic Proteins; D026901:Membrane Transport Proteins; C484549:SLC33A1 protein, human
SLC33A1; exome sequencing; hereditary spastic paraplegias (HSP); mutation