Mutation analysis of four Chinese families with pure hereditary spastic paraplegia: pseudo- X-linked dominant inheritance and male lethality due to a novel ATL1 mutation.

ABSTRACT

We studied four Chinese families with pure hereditary spastic paraplegia (HSP) to investigate the clinical features and associated genetic mutations. Linkage analysis was performed for all families to map the disease locus onto autosomal chromosomes, and related loci involved in HSP on the X chromosome were also examined. Polymerase chain reaction (PCR) sequencing was used to detect gene mutations. To confirm the influence of a splice-site mutation on mRNA, we used reverse transcription-PCR and direct sequencing. Linkage analysis and ATL1 gene sequencing of amniocytes were performed for prenatal genetic diagnosis. One missense variant (c.1517T>A) and a splice-site mutation (c.1245+1G>A) in SPAST, and two missense variants (c.715C>T, c.1204T>G) in ATL1 were identified. The c.1245+1G>A mutation caused a deletion of exon 9 in the SPAST gene. Prenatal genetic diagnosis showed that fetus did not carry the ALT1 c.1204T>G mutation. Follow-up was maintained for 5 years, and the negative result was confirmed by evidence of a healthy growing boy. We identified two novel mutations and two previously reported mutations in SPAST and ATL1, respectively. The family with the ATL1 c.1204T>G mutation exhibited male-lethality, female infancy-onset, and pseudo- X-linked dominant transmission, which had never been previously reported for HSP. Characteristic facial features were also noticed. The boy on whom prenatal gene diagnosis was performed is healthy and without unusual facies, suggesting that the c.1204T>G mutation might be related to these features. The results extend the genetic spectrum of HSP and suggest that linkage analysis remains a powerful tool in gene discovery studies.