Allele-specific expression at the androgen receptor alpha gene in a hybrid unisexual fish, the Amazon molly (Poecilia formosa)

Abstract

The all-female Amazon molly (Poecilia formosa) is the result of a hybridization of the Atlantic molly (P. mexicana) and the sailfin molly (P. latipinna) approximately 120,000 years ago. As a gynogenetic species, P. formosa needs to copulate with heterospecific males including males from one of its bisexual ancestral species. However, the sperm only triggers embryogenesis of the diploid eggs. The genetic information of the sperm donor typically will not contribute to the next generation of P. formosa. Hence, P. formosa possesses generally one allele from each of its ancestral species at any genetic locus. This raises the question whether both ancestral alleles are equally expressed in P. formosa. Allele-specific expression (ASE) has been previously assessed in various organisms, e.g., human and fish, and ASE was found to be important in the context of phenotypic variability and disease. In this study, we utilized Real-Time PCR techniques to estimate ASE of the androgen receptor alpha (arα) gene in several distinct tissues of Amazon mollies. We found an allelic bias favoring the maternal ancestor (P. mexicana) allele in ovarian tissue. This allelic bias was not observed in the gill or the brain tissue. Sequencing of the promoter regions of both alleles revealed an association between an Indel in a known CpG island and differential expression. Future studies may reveal whether our observed cis-regulatory divergence is caused by an ovary-specific trans-regulatory element, preferentially activating the allele of the maternal ancestor.

Nonadditive and Asymmetric Allelic Expression of Growth Hormone in Hybrid Tilapia

“…All-female Amazon molly was generated by distant hybridization of the Atlantic molly ( Poecilia mexicana ) and the sailfin molly ( Poecilia latipinna ). The ASE analysis of androgen receptor α suggested a maternal bias in ovary from Amazon molly (Zhu et al, 2017a). There were high ratios of maternal homolog expression of transcripts in diploid and tetraploid hybrids of Carassius auratus red var.…”

The gonadal transcriptome of the unisexual Amazon molly Poecilia formosa in comparison to its sexual ancestors, Poecilia mexicana and Poecilia latipinna

“…Here, meiosis and recombination are maintained (e.g., in whiptail lizards, [ 87 ]). In contrast, our ameiotic species lacks recombination and is hence a ‘frozen hybrid’ at all nuclear loci [ 18 , 33 , 88 ].…”

Identification and effective regulation of <i>scarb1</i> gene involved in pigmentation change in autotetraploid <i>Carassius auratus</i>

“…Interestingly, analysis of allele-specific expression (ASE) revealed that scarb1 was detected in both RCC (85.7% for scarb1a-A and 14.3% for scarb1a-B ; 12.5% for scarb1b-A and 87.5% for scarb1b-B ) and 4nRR (76.9% for scarb1a-A , 73.3% for scarb1b-A , and 60% for scarb1c-A ). ASE, often driven by cis-regulatory elements, is a common event in various animal species, including humans, mice, chickens, Amazon mollies, California tiger salamanders, and hybrid tilapias ( Cooper & Shaffer, 2021 ; Lagarrigue et al, 2013 ; Lo et al, 2003 ; Song et al, 2012b ; Zhou et al, 2019 ; Zhu et al, 2017 ; Zhuo et al, 2017 ). These occurrences have been linked to disease risk and phenotypic severity of disease-causing CDS variants.…”