Autosomal recessive congenital cataract in captive-bred vervet monkeys (Chlorocebus aethiops)

Proprotein convertase subtilisin/kexin type 9 genetic screening using the vervet (Chlorocebus aethiops) model

BACKGROUND

The proprotein convertase subtilisin/kexin type 9 (PCSK9) gene has come to prominence due to its reported function in the clearance of low-density lipoprotein cholesterol. The vervet monkey (Chlorocebus aethiops) was utilized to study the genetics of PCSK9 gene.

METHOD

Sixteen vervet monkeys were selected to screen for possible PCSK9 polymorphisms and to determine gene expression.

RESULTS

Four PCSK9 sequence variants (T112T, R148S, H177N and G635G) were identified and three of these variants (H177N, R148S, and G635G) were categorized as loss of function mutations. A decline in gene expression levels was also observed in animals harboring these three variants. Although the selected variants might have affected the level of gene expression in the selected animals, individual variation was also noticed in some of these individuals with the G635G variant.

CONCLUSION

Based on the findings obtained from this study, it is suggestive that the activity of PCSK9 was hindered.

Mutational analysis of BFSP1, CRYBB1, GALK1, and GJA8 in captive-bred vervet monkeys (Chlorocebus aethiops)

BACKGROUND

Congenital cataract has been reported in a colony of captive-bred vervet monkeys (Chlorocebus aethiops).

METHODS

Molecular tools such as genotyping and gene expression were used to identify mutations associated with congenital cataract in this vervet colony. Beaded filament structural protein 1 (BFSP1), beta-crystallin B1 (CRYBB1), galactokinase1 (GALK1), and gap junction alpha-8 protein (GJA8) were screened, sequenced, and analyzed for mutations in 24 vervet monkeys (control and cataract).

RESULTS

Five missense sequence variants were identified (V147E, A167P, L212F, N55K, and T247A), three of which were found to be potentially disease-causing. Furthermore, downregulation was observed in BFSP1, CRYBB1, and GALK1 genes.

CONCLUSION

This study reports two cases of incomplete penetrance and/or uniparental disomy (L212F and T247A) in BSFP1. Mutations in BSFP1 together with three mutations in GALK1 and GJA8 were predicted to be disease-causing.

The effect of hyperglycinemic treatment in captive-bred Vervet monkeys (Chlorocebus aethiops)

Nonketotic hyperglycinemia (NKH) is a neuro-metabolic disorder caused by a deficiency in the glycine cleavage system (GCS) and glycine transporter 1 (GlyT1). A case of atypical late onset of NKH has been reported in a colony of captive-bred Vervet monkeys. The purpose of this study was to evaluate the effect of sodium benzoate and dextromethorphan in reducing glycine levels in hyperglycinemic monkeys. Twelve captive-bred Vervet monkeys were assigned into three groups consisting of four animals (control, valproate induced and cataract with spontaneous hyperglycinemia). Valproate was used to elevate glycine levels and the induced group was then treated with sodium benzoate and dextromethorphan together with group three to normalise glycine levels in cerebrospinal fluid (CSF) and plasma. Valproate induction elicited changes in phosphate, alkaline phosphatase and platelet count, however, no significant changes in the glycine levels were observed, and this might be due to the individual variability within the group. The treatment intervention was only obtained in the spontaneous group whereby the glycine levels were normalised in CSF and plasma. Therefore, it can be concluded that sodium benzoate and dextromethorphan treatment was effective and beneficial to the hyperglycinemic group.

Nonketotic hyperglycinemia in captive-bred Vervet monkeys (Chlorocebus aethiops) with cataracts

BACKGROUND

Nonketotic hyperglycinemia (NKH) is a rare metabolic disorder that is characterized by high levels of glycine in plasma and cerebrospinal fluid in humans. In this study, total congenital cataract captive-bred Vervet monkeys (Chlorocebus aethiops) that are hyperglycinemic were screened to identify mutations in Bola type 3 (BOLA3), glutaredoxin 5 (GLRX5), and lipoate synthase (LIAS) genes.

METHODS

Twenty-four Vervet monkeys (12 hyperglycinemic and 12 healthy controls) were selected for mutation analysis using polymerase chain reaction (PCR), Sanger sequencing, and reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Novel sequence variants were identified in BOLA3 (R23H and Q38R) and LIAS (R369I and A371A), and gene expression in the control group was significantly lower compared to the hyperglycinemic group (P < 0.05).

CONCLUSION

The data obtained from this study will contribute to generation of new knowledge regarding the involvement of these genes in NKH development.