title: Allelic variant in the anti-Müllerian hormone gene leads to autosomal and temperature-dependent sex reversal in a selected Nile tilapia line.
abstract: Owing to the demand for sustainable sex-control protocols in aquaculture, research in tilapia sex determination is gaining momentum. The mutual influence of environmental and genetic factors hampers disentangling the complex sex determination mechanism in Nile tilapia (Oreochromis niloticus). Previous linkage analyses have demonstrated quantitative trait loci for the phenotypic sex on linkage groups 1, 3, and 23. Quantitative trait loci for temperature-dependent sex reversal similarly reside on linkage group 23. The anti-Müllerian hormone gene (amh), located in this genomic region, is important for sexual fate in higher vertebrates, and shows sexually dimorphic expression in Nile tilapia. Therefore this study aimed at detecting allelic variants and marker-sex associations in the amh gene. Sequencing identified six allelic variants. A significant effect on the phenotypic sex for SNP ss831884014 (p<0.0017) was found by stepwise logistic regression. The remaining variants were not significantly associated. Functional annotation of SNP ss831884014 revealed a non-synonymous amino acid substitution in the amh protein. Consequently, a fluorescence resonance energy transfer (FRET) based genotyping assay was developed and validated with a representative sample of fish. A logistic linear model confirmed a highly significant effect of the treatment and genotype on the phenotypic sex, but not for the interaction term (treatment: p<0.0001; genotype: p<0.0025). An additive genetic model proved a linear allele substitution effect of 12% in individuals from controls and groups treated at high temperature, respectively. Moreover, the effect of the genotype on the male proportion was significantly higher in groups treated at high temperature, giving 31% more males on average of the three genotypes. In addition, the groups treated at high temperature showed a positive dominance deviation (+11.4% males). In summary, marker-assisted selection for amh variant ss831884014 seems to be highly beneficial to increase the male proportion in Nile tilapia, especially when applying temperature-induced sex reversal.
authors.affiliation: Department of Animal Sciences - Aquaculture and Water Ecology, Goettingen University, Goettingen, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Wessels
authors.affiliation: Department of Animal Sciences - Animal Breeding and Genetics, Goettingen University, Goettingen, Germany.
authors.forename: Reza Ahmad
authors.initials: RA
authors.lastname: Sharifi
authors.affiliation: Department of Animal Sciences - Aquaculture and Water Ecology, Goettingen University, Goettingen, Germany.
authors.forename: Liane Magdalena
authors.initials: LM
authors.lastname: Luehmann
authors.affiliation: Department of Animal and Aquatic Sciences, Faculty of Agriculture, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Sawichaya
authors.initials: S
authors.lastname: Rueangsri
authors.affiliation: Department of Animal Sciences - Aquaculture and Water Ecology, Goettingen University, Goettingen, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Krause
authors.affiliation: Department of Animal Sciences - Molecular Biology and Molecular Diagnostics of Livestock, Goettingen University, Goettingen, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pach
authors.affiliation: Department of Animal Sciences - Aquaculture and Water Ecology, Goettingen University, Goettingen, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Hoerstgen-Schwark
authors.affiliation: Department of Animal Sciences - Livestock Biotechnology and Reproduction, Goettingen University, Goettingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Knorr
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D054304:Anti-Mullerian Hormone / Q000235:genetics*; D001483:Base Sequence; D023681:Cichlids / Q000235:genetics / Q000502:physiology*; D005260:Female; D005838:Genotype; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D019849:Sex Determination Processes; D013696:Temperature
chemical_list: D054304:Anti-Mullerian Hormone