Asparagine synthetase deficiency detected by whole exome sequencing causes congenital microcephaly, epileptic encephalopathy and psychomotor delay

Salma Ben-Salem, Joseph G. Gleeson, Aisha M. Al-Shamsi, Barira Islam, Jozef Hertecant, Bassam R. Ali, Lihadh Al-Gazali

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Deficiency of Asparagine Synthetase (ASNSD, MIM 615574) is a very rare autosomal recessive disorder presenting with some brain abnormalities. Affected individuals have congenital microcephaly and progressive encephalopathy associated with severe intellectual disability and intractable seizures. The loss of function of the asparagine synthetase (ASNS, EC 6.3.5.4), particularly in the brain, is the major cause of this particular congenital microcephaly. In this study, we clinically evaluated an affected child from a consanguineous Emirati family presenting with congenital microcephaly and epileptic encephalopathy. In addition, whole-exome sequencing revealed a novel homozygous substitution mutation (c.1193A > C) in the ASNS gene. This mutation resulted in the substitution of highly conserved tyrosine residue by cysteine (p.Y398C). Molecular modeling analysis predicts hypomorphic and damaging effects of this mutation on the protein structure and altering its enzymatic activity. Therefore, we conclude that the loss of ASNS function is most likely the cause of this condition in the studied family. This report brings the number of reported families with this very rare disorder to five and the number of pathogenic mutations in the ASNS gene to four. This finding extends the ASNS pathogenic mutations spectrum and highlights the utility of whole-exome sequencing in elucidation the causes of rare recessive disorders that are heterogeneous and/or overlap with other conditions.

Original languageEnglish
Pages (from-to)687-694
Number of pages8
JournalMetabolic Brain Disease
Volume30
Issue number3
Early online date17 Sep 2014
DOIs
Publication statusPublished - 1 Jun 2015
Externally publishedYes

Fingerprint

Aspartate-Ammonia Ligase
Exome
Microcephaly
Brain Diseases
Brain
Substitution reactions
Genes
Mutation
Molecular modeling
Cysteine
Tyrosine
asparagine synthetase (glutamine-hydrolyzing)
Proteins
Intellectual Disability
Seizures

Cite this

Ben-Salem, Salma ; Gleeson, Joseph G. ; Al-Shamsi, Aisha M. ; Islam, Barira ; Hertecant, Jozef ; Ali, Bassam R. ; Al-Gazali, Lihadh. / Asparagine synthetase deficiency detected by whole exome sequencing causes congenital microcephaly, epileptic encephalopathy and psychomotor delay. In: Metabolic Brain Disease. 2015 ; Vol. 30, No. 3. pp. 687-694.
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Asparagine synthetase deficiency detected by whole exome sequencing causes congenital microcephaly, epileptic encephalopathy and psychomotor delay. / Ben-Salem, Salma; Gleeson, Joseph G.; Al-Shamsi, Aisha M.; Islam, Barira; Hertecant, Jozef; Ali, Bassam R.; Al-Gazali, Lihadh.

In: Metabolic Brain Disease, Vol. 30, No. 3, 01.06.2015, p. 687-694.

Research output: Contribution to journalArticle

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AB - Deficiency of Asparagine Synthetase (ASNSD, MIM 615574) is a very rare autosomal recessive disorder presenting with some brain abnormalities. Affected individuals have congenital microcephaly and progressive encephalopathy associated with severe intellectual disability and intractable seizures. The loss of function of the asparagine synthetase (ASNS, EC 6.3.5.4), particularly in the brain, is the major cause of this particular congenital microcephaly. In this study, we clinically evaluated an affected child from a consanguineous Emirati family presenting with congenital microcephaly and epileptic encephalopathy. In addition, whole-exome sequencing revealed a novel homozygous substitution mutation (c.1193A > C) in the ASNS gene. This mutation resulted in the substitution of highly conserved tyrosine residue by cysteine (p.Y398C). Molecular modeling analysis predicts hypomorphic and damaging effects of this mutation on the protein structure and altering its enzymatic activity. Therefore, we conclude that the loss of ASNS function is most likely the cause of this condition in the studied family. This report brings the number of reported families with this very rare disorder to five and the number of pathogenic mutations in the ASNS gene to four. This finding extends the ASNS pathogenic mutations spectrum and highlights the utility of whole-exome sequencing in elucidation the causes of rare recessive disorders that are heterogeneous and/or overlap with other conditions.

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