Abstract
Background: Asparagine Synthetase Deficiency (ASNSD; OMIM #615574) is a newly described rare autosomal recessive neurometabolic disorder, characterised by congenital microcephaly, severe psychomotor delay, encephalopathy and progressive cerebral atrophy. To date, seven families and seven missense mutations in the ASNSD disease causing gene, ASNS, have been published. Methods: We report two further affected infant sisters from a consanguineous Indian family, who in addition to the previously described features had diaphragmatic eventration. Both girls died within the first 6 months of life. Whole exome sequencing (WES) was performed for both sisters to identify the pathogenic mutation. The clinical and biochemical parameters of our patient are compared to previous reports. Results: WES demonstrated a homozygous novel missense ASNS mutation, c.1019G > A, resulting in substitution of the highly conserved arginine residue by histidine (R340H). Conclusion: This report expands the phenotypic and mutation spectrum of ASNSD, which should be considered in neonates with congenital microcephaly, seizures and profound neurodevelopmental delay. The presence of diaphragmatic eventration suggests extracranial involvement of the central nervous system in a disorder that was previously thought to exclusively affect the brain. Like all previously reported patients, these cases were diagnosed with WES, highlighting the clinical utility of next generation sequencing in the diagnosis of rare, difficult to recognise disorders.
Competing interests: None declared
Please note that Jun Sun and Angela J. McGillivray contributed equally and should be shared first authors. Maya Chopra and Asan should be co-corresponding authors.
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Communicated by: Verena Peters
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Fig. 1
Sequence alignment of the ASNS protein between human and E.coli. AsnB and ASNS (TIFF 925 kb)
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Concise Synopsis
A novel homozygous mutation in ASNS causes asparagine synthetase deficiency in two sisters with microcephaly, severe psychomotor delay, cerebral atrophy and diaphragmatic hernia.
Authors’ Contributions
Jun Sun was responsible for the NGS experiment, interpretation of mutation data and drafting the relevant part of manuscript.
Angela J McGillivray, Jason Pinner, Drago Bratkovic and Elizabeth Thompson drafted the relevant parts of manuscript and critically revised the paper.
Fengxia Liu performed the bioinformatic analysis of the NGS data.
Zhihui Yan and Huifeng Jiang performed and interpreted the protein simulation experiment.
Xiuxiu Wei performed and interpreted the Sanger sequencing experiment.
Asan was responsible for the experiment resign and reviewed the manuscript.
Maya Chopra was responsible for the study conception and design, the drafting of the manuscript.
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Asan.
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Maya Chopra has received a reimbursement from BGI as an invited speaker to a conference sponsored by BGI.
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The parents of the patients have consented to take part in this study. They have consented to the publication of this paper. Consent for photographs was declined. There are no photographs in this paper.
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Sun, J. et al. (2016). Diaphragmatic Eventration in Sisters with Asparagine Synthetase Deficiency: A Novel Homozygous ASNS Mutation and Expanded Phenotype. In: Morava, E., Baumgartner, M., Patterson, M., Rahman, S., Zschocke, J., Peters, V. (eds) JIMD Reports, Volume 34. JIMD Reports, vol 34. Springer, Berlin, Heidelberg. https://doi.org/10.1007/8904_2016_3
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DOI: https://doi.org/10.1007/8904_2016_3
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