Mutation detectionin the endoglin gene in a family with hereditary haemorrhagic telangiectasia
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Date
2017-12
Authors
Peta, Kimberly Thando
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
Introduction: Hereditary haemorrhagic telangiectasia (HHT) is a rare autosomal
dominant bleeding disorder. It is characterised by the presence of mucocutaneous
telangiectases, visceral arteriovenous malformations and epistaxis. The phenotype is
diagnosed according to the Curaçao criteria. At a molecular level, HHT has been
linked to the Endoglin, Activin kinase 1 (ALK1) and SMAD4 genes in numerous
studies. The majority of studies are centred on European and American population
groups. There are few publications of HHT on people of African descent, none of
which are family based studies. To our knowledge, this is the first study presenting
mRNA expression sequence data of the Endoglin (ENG) gene in a population of
African descent. The aim of the study is to detect splice site and exon region
mutations present in the ENG gene of the family members affected with HHT.
Methodology: RNA was isolated from blood, stabilised in RNAlater and stored at -
20ºC using the Ribopure blood kit and TRizol® methods. The RNA was converted to
cDNA that served as a template molecule for sequence mutation detection. In total
11 primer pairs were designed and used to amplify 15 exon regions of the endoglin
gene. Sanger sequencing was employed to determine ENG mutations. Results:
Four mutations were identified, two in exon 1, namely c.-324A>G and c.-207G>A
and two missense mutations c.640G>A and c.1510G>A located in exon 5 and exon
11 were identified, respectively. The exon 1 mutation c.-324A>G is a population
variant. The c.-207G>A exon 1 mutation was concluded to have no effect on the
resulting amino acid and only one HHT individual harboured this mutation. The
missense mutations c.640G>A and c.1510G>A were previously described in
participants with and without HHT in literature, resulting in conflicting interpretations
regarding HHT causality. Results from this study indicate that the latter mutations
occurred in two different individuals that have been diagnosed with HHT.
Conclusion: The identified mutations were present in individuals who were formerly
diagnosed with HHT but none of them can be proven to be pathogenic, since it was
not present in all the HHT affected family members. Future studies should focus on
the mutation detection of other HHT associated genes such as SMAD4, ALK1,
BMP9 and RASA1 genes in this family to decipher HHT pathogenesis in a family
from African descent.
Description
Keywords
Genetics, Splice site, HHT, Vasculogenesis, Angiogenesis, Haemorrhagic, Telangiectases, AVM, Africa, Mutations, Dissertation (M.Sc. (Genetics))--University of the Free State, 2017