Exome sequencing of a Pakistani family with spastic paraplegia identified an 18 bp deletion in the cytochrome B5 domain of FA2H

ABSTRACT

Hereditary spastic paraplegias (HSPs) are a diverse class of neurodegenerative disorders that mainly affect the corticospinal tract of the body and result in various clinical conditions such as lower limb spasticity and muscle weakness in the lower extremities. Worldwide, more than 70 chromosomal loci/genes have been reported to be associated with HSPs, out of which, six genes viz., ATL1, FA2H, GJC2, AP4E1, ALDH18A1 and ATP13A2 have been mapped in Pakistani families. In the present genetic study, we report on a large consanguineous Pakistani family with a complex form of HSP segregating with a 18 bp deletion in the first exon of the Fatty Acid 2-Hydroxylase (FA2H) gene (NM_024306.5:c.159_176del). The identified in-frame deletion results in loss of six amino acids (p.Arg53_Ile58del) within the cytochrome B5 domain of the protein. FA2H is required for alpha-hydroxylation of free fatty acids to form alpha-hydroxylated sphingolipids. Its cytochrome b5-like heme-binding domain, which spans from residues 15 to 85, imparts the redox activity to FA2H. This mutation has previously been reported in a Pakistani family presenting with a similar form of complex HSP. Together with our findings the pathogenic role of the observed variant is further supported. Mutation studies on additional Pakistani families for FA2H will further elucidate its mutational spectrum, which may help in developing a prenatal diagnostic test for Khyber Pakhtunkhwa resident Pakistani families.

KEYWORDS:

• Hereditary Spastic Paraplegia
• Pakistani family
• FA2H
• cytochrome B5 domain
• deletion mutation

Authors contributions

SA, BB, JB & BT, JW performed experiments and data analysis, MZ & KR recruited the family and did clinical analysis, SG did bioinformatic predictions, MAK, and CW remained involved in data analysis, manuscript drafting & project supervision. All authors have read, edited, and approved the final version of manuscript.

Acknowledgments

We are grateful to all the family members for their volunteer participation in the present genetic study. MAK is thankful to Higher Education Commission of Pakistan for supporting the present study through an NPRU grant (5564/KPK/NRPU/R&D/HEC/2016).

Disclaimer

No part of this manuscript has been presented or published in any journal, except its inclusion in M.Phil thesis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Safdar Abbas

Safdar Abbas, he did his BS (Session 2010-14) from Gomal Centre of Biochemistry and Biotechnology, Gomal University, D.I.Khan. Pakistan and then from same department he accomplished his Master in Human Genetics.

Beatrice Brugger

Beatrice Brugger, she did her Master in Biochemistry and Molecular Biology at the Technical University of Graz. Additionally, she graduated her second Master in Medical Genetics at the Medical University of Graz. At present she is doing her PhD in Placental Research at the Institute for Histology, Cell biology and Embryology at the Medical University of Graz.

Muhammad Zubair

Muhammad Zubair, he did his BS (Session 2009-13) from Gomal Centre of Biochemistry and Biotechnology, Gomal University, D.I.Khan. Pakistan and later he completed his Master in Human Genetics from University of Science and Technology, China. Currently, he is doing Ph.D. from same institute in China.

Sana Gul

Sana Gul, she did her BS (Session 2010-14) from Gomal Centre of Biochemistry and Biotechnology, Gomal University, D.I.Khan. Pakistan and later she accomplished her Master in Biotechnology from International Islamic University, Islamabad, Pakistan.

Jasmin Blatterer

Jasmin Blatterer, She completed graduate studies in biochemistry and molecular biomedicine at the University of Graz/Austira and currently works as a research assistant at the Diagnostic and Research Institute of Human Genetics, Medical University of Graz/Austria where she is also enrolled in an extra-occupational PhD program.

Julian Wenninger

Julian Wenninger, after his graduation as a MD from the Medical University of Graz in 2014, he was awarded a PhD in Laboratory Medicine by this institution in 2020. Since then, he is continuing his residency in Child and Adolescent Psychiatry with a keen interest in genetic causes and ethical aspects of treatment.

Khurram Rehman

Khurram Rehman, he earned his Pharm D from Faculty of Pharmacy, Gomal University, D.I.Khan. Pakistan and later from same department he earned his Ph.D. in Pharmaceutical Sciences. Currently, he is working in APEX institute of Medical Sciences, D.I.Khan, Pakistan.

Benjamin Tatrai

Benjamin Tatrai, he is currently student at the Medical University of Graz.

Muzammil Ahmad Khan

Muzammil Ahmad Khan, he did his masters from Quaid-i-Azam University, Islamabad, Pakistan in Biochemistry and Molecular Biology, later from same department he accomplished his Doctoral studies in Human Molecular Genetics. Thereafter, he also worked in Translational Research Institute of Hamad Medical Corporation, Doha, Qatar as Postdoc research scientist. Currently, he is working as an Assistant Professor at Gomal University, Pakistan.

Christian Windpassinger

Christian Windpassinger, he did his masters and PhD in Biology/Genetics at the Paris Lodron University in Salzburg/Austria. Afterwards, he worked as a research assistant at the Institute for Medical Biology at the Karl Franzens University of Graz/Austria. After a post-Doctoral stay at the Centre for Addiction and Mental Health in Toronto/Canada he moved back to Graz, where he currently holds the position of an Associate Professor at the Diagnostic and Research Institute of Human Genetics, Medical University of Graz/Austria.