>Magister Scientiae - MSc / Molecular genetics: strategies to indentify congenital cataract genes in captive-bred Vervet
monkeys
Zandisiwe Emilia Magwebu
MSc thesis, Department of Medical Biosciences, University of the Western Cape
The present study describes molecular aspects of inherited congenital cataract in captive-bred
Vervet monkeys. Congenital cataracts are lens opacities that are present at birth or soon after
birth and include hereditary cataracts or cataracts caused by infectious agents. The MRC Primate
Unit is housing a colony of captive-bred Vervet monkeys in which 7.5% is suffering from
congenital cataract. However, the parents of the affected individuals were asymptomatic. Six
families within the colony have been identified to be affected by two types of morphologies (Ysutural
and total cataract). Based on the evidence provided above, it was speculated that the
colony was affected with autosomal recessive cataract.
The main aim of this study was to facilitate a strategy for managing breeding programs by
minimizing cataract occurrences in captive-bred Vervet monkeys. Integrated combination of
clinical, molecular and bioinformatic strategies were used to identify and assess reciprocal
candidate susceptibility genes for cataracts. The genes that are known to be responsible for most
human congenital cataract cases were prioritized. The genes include Heat shock transcription
factor 4 (HSF4), Crystalline Alpha A (CRYAA), glucosaminyl (N-acetyl) transferase 2 (GCNT2) and Lens intrinsic membrane protein 2 (LIM2). Twenty two subjects were selected based on their
morphology (5 carriers, 5 controls and 12 cataracts). 2ml of blood was collected for
Deoxyribonucleic acid (DNA) extraction. Coding exons and flanking regions were screened by
polymerase chain reaction (PCR) amplification and sequenced. The CLC DNA workbench was
used for results analysis.
The screening of four genes revealed 20 sequence variants which were not present in the control
individuals. Sequencing of HSF4 revealed three mutations: R116R, L245>L and P421>L in exon
5, 10 and 14, respectively. The coding exons for CRYAA showed two sequence variants: S134W
and K166N in exon 3. Twelve mutations were identified in exon one of all three GCNT2
transcripts (A, B and C). These mutations include: G212G, H256>H, M258>V, N275>N, V16>I,
Y122>F, S15>S, S24>N, S38>S, I118>I, D194>D and Y373>Y which was found in exon three
of all transcripts. There were no mutations in LIM2, however, three single nucleotide
polymorphisms (SNPs) were identified in exon 2 (P66>P) and 3 (I118>T and A127>T). The
above mutations were conserved when aligned with other species. The sequence variations vary
among the families and those individuals with the same or different cataract phenotype.
Based on these findings, it can be concluded that the four candidate genes harbour mutations that
are responsible for both phenotypes. The effect of these mutations in Vervet monkeys is not yet
understood, however, their impact will be further investigated. For future studies, it will be of
absolute importance to screen the entire family to verify that indeed cataract formation in this
colony is inherited in an autosomal recessive manner.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/4265 |
| Date | January 2013 |
| Creators | Magwebu, Zandisiwe Emilia Z.E. |
| Contributors | Seier, Jurgen |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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