# GH1 Gene Polymorphisms Reveal Population-Level Allele Variation in North African (Clarias gariepinus) and Bighead Catfish (Clarias macrocephalus)

## TL;DR

This study examines genetic variations in the GH1 gene of two catfish species to understand their growth differences and genetic origins.

## Contribution

The study identifies six GH1 gene alleles and reveals lineage-specific variations and purifying selection in catfish populations.

## Key findings

- Six GH1 alleles were identified with 33 variable sites in intron 2.
- Low heterozygosity was observed in GH1 across populations.
- Bayesian clustering revealed two distinct genetic clusters for the catfish species.

## Abstract

Background/Objectives: North African catfish (Clarias gariepinus) and bighead catfish (Clarias macrocephalus) play crucial roles in Thai aquaculture. Although significant growth disparities exist among these species, the genetic factors underlying these differences are still unknown. This study aimed to identify GH1 gene polymorphisms, in North African and bighead catfish populations across Thailand and Laos. Methods: Sequencing, phylogenetic, and clustering analyses were performed to assess genetic diversity, selection patterns, and lineage differentiation of catfish partial GH1 fragment. Results: Six alleles of the studied fragment of GH1 gene were identified; they differed at 33 variable sites within intron 2, located between the conserved regions at the 3′ end of exon 2 and the 5′ end of exon 3. At the population-level, GH1 exhibited low heterozygosity (mean Ho = 0.043 ± 0.023; He = 0.059 ± 0.028). Bayesian clustering analyses identified two distinct genetic clusters, corresponding to North African and bighead catfish, apart from the bighead population in Laos, indicating their distinct genetic origins. Evidence of purifying selection was observed in both species. Phylogenetic analysis indicated the presence of lineage-specific alleles in the GH1 gene. Conclusions: These findings provide valuable insights into GH1 polymorphisms in commercially important catfish species and may help to develop future breeding programs aimed at enhancing aquaculture productivity.