Characterizing asparagine synthetase deficiency variants in lymphoblastoid cell lines

Staklinski, Stephen J, Chang, Mario C, Ahrens-Nicklas, Rebecca C, Kaur, Shagun, Stefanatos, Arianna K, Dudenhausen, Elizabeth E, Merritt, Matthew E, Kilberg, Michael S (March 2023) Characterizing asparagine synthetase deficiency variants in lymphoblastoid cell lines. JIMD Reports, 64 (2). pp. 167-179. ISSN 2192-8304

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Abstract

Asparagine synthetase (ASNS) catalyzes the synthesis of asparagine (Asn) from aspartate and glutamine. Biallelic mutations in the ASNS gene result in ASNS Deficiency (ASNSD). Children with ASNSD exhibit congenital microcephaly, epileptic-like seizures, and continued brain atrophy, often leading to premature mortality. This report describes a 4-year-old male with global developmental delay and seizures with two novel mutations in the ASNS gene, c.614A > C (maternal) and c.1192dupT (paternal) encoding p.H205P and p.Y398Lfs*4 variants, respectively. We employed the novel use of immortalized lymphoblastoid cell lines (LCL) to show that the proliferation of the heterozygotic parental LCL was not severely affected by culture in Asn-free medium, but growth of the child's cells was suppressed by about 50%. Asn production by the LCL from both the father and the child was significantly decreased relative to the mother's cells. mRNA and protein analysis of the paternal LCL cells for the Y398Lfs*4 variant revealed reductions in both. Attempts to ectopically express the truncated Y398Lfs*4 variant in either HEK293T or ASNS-null cells resulted in little or no detectable protein. Expression and purification of the H205P variant from HEK293T cells revealed enzymatic activity similar to wild-type ASNS. Stable expression of WT ASNS rescued the growth of ASNS-null JRS cells in Asn-free medium and the H205P variant was only slightly less effective. However, the Y398Lfs*4 variant appeared to be unstable in JRS cells. These results indicate that co-expression of the H205P and Y398Lfs*4 variants leads to a significant reduction in Asn synthesis and cellular growth.

Item Type:	Paper
Subjects:	diseases & disorders diseases & disorders > nervous system diseases and disorders diseases & disorders > nervous system diseases and disorders > epilepsy
CSHL Authors:	Staklinski, Stephen
Communities:	CSHL labs > Siepel lab School of Biological Sciences > Publications
SWORD Depositor:	CSHL Elements
Depositing User:	CSHL Elements
Date:	March 2023
Date Deposited:	01 Nov 2023 17:25
Last Modified:	29 Feb 2024 18:10
PMCID:	PMC9981421
Related URLs:	Publisher
URI:	https://repository.cshl.edu/id/eprint/41292

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