Biology subjects

Norberg, B.

Publications and source records attributed to Norberg, B..

3 recordsLinked to original sources

bioRxiv2026

Vgll3a promotes sexual maturation in male and female Atlantic salmon

The age at which Atlantic salmon reaches sexual maturity shows a strong hereditary component associated with the vgll3a locus. The role of Vgll3 in maturation has remained unknown in vertebrates until recently, when it has been linked to pleiotropic roles in killifish, both delaying male maturation and affecting lifespan by protecting against cancer. As Atlantic salmon has two vgll3 paralogs, where only vgll3a has been associated with sexual maturation, it may provide a suitable model for studying the maturation-specific function of vgll3, as the other paralog may buffer for pleiotropic roles of vgll3. To address this, we used CRISPR/Cas9 to generate fish highly mutated in the vgll3a gene. We monitored their maturation and crossed highly mutated crispants to generate two year-classes of complete loss-of-function. All groups were reared under environmental conditions triggering early maturation in one-year-old males. We found a clear difference in the proportion of sexually maturing or mature fish between the different genotypes: in all experiments significantly fewer vgll3a-/- males entered puberty and reached final maturation compared to vgll3a+/- and vgll3a+/+ males. Furthermore, loss of vgll3a resulted in lower frequencies of maturation also in females. We conclude that Vgll3a stimulates maturation and that its complete removal significantly reduced maturation rates in both sexes in Atlantic salmon. Our findings also identify vgll3a as the causative gene in the locus associated with age at sexual maturity. Together, our findings support a new role for Vgll3 in initiating puberty in vertebrates and identifying salmon as a promising model for functional studies regarding the timing of sexual maturation.

genomics↗

bioRxiv2022

Molecular mechanisms involved in Atlantic halibut (Hippoglossus hippoglossus) egg quality: impairments at transcription and protein folding levels induce inefficient protein and energy homeostasis during early development

BackgroundReproductive success and normal development in all animals are dependent on egg quality and developmental competence of the produced embryo. This study employed tandem mass tags labeling based liquid chromatography tandem mass spectrometry for egg proteomic profiling to investigate differences in the global proteome of good versus poor quality Atlantic halibut eggs at 1-cell stage post fertilization. ResultsA total of 115 proteins were found to be differentially abundant between good and poor quality eggs. Frequency distribution of these proteins revealed higher protein folding activity in good quality eggs in comparison to higher transcription and protein degradation activities in poor quality eggs (p < 0.05). Poor quality halibut eggs were significantly enriched with additional proteins related to mitochondrial structure and biogenesis (p < 0.05). The differential abundance of a selection of proteins was first confirmed at gene expression level using a transcriptomic approach followed by a targeted proteomic approach (parallel reaction monitoring based mass spectrometry) in biological samples obtained from two consecutive reproductive seasons. The findings of global proteome profiling, together with the validation of differential abundance of targeted proteins and their related genes, suggest impairments in protein and energy homeostasis which might be related to unfolded protein response and mitochondrial stress in poor quality eggs. Additional transmission electron microscopy studies were taken to assess potential differences in abundance and morphological integrity of mitochondria between good and poor quality eggs. Observations reveal poor quality eggs to contain significantly higher number of mitochondria with higher number of cristae. These mitochondria, however, are significantly smaller and have a more irregular shape than those found in high-quality eggs. Therewithal difference in mtDNA levels represented by mt-nd5 and mt-atp6 genomic DNA abundance in this study, were found to be not statistically significant (p > 0.05) between good and bad quality eggs at both 1 hpf and 24 hpf stages. ConclusionOverall evidence from this study indicate that poor quality eggs undergo impairments at both transcription and translation level leading to endoplasmic reticulum and mitochondrial deficiencies. Additional research may be required to expediate the details and the potential of these impairments occurring in different species. Nonetheless, this study will pave the way for future research and will help in acceleration of recent advances in the field of embryonic developmental competence of living organisms.

molecular biology↗

bioRxiv2020

Heterochiasmy facilitated the establishment of gsdf as a novel sex determining gene in Atlantic halibut

Atlantic Halibut (Hippoglossus hippoglossus) has a X/Y genetic sex determination system, but the sex determining factor is not known. We produced a high-quality genome assembly and identified parts of chromosome 13 as the Y chromosome due to sequence divergence between sexes and segregation of sex genotypes in pedigrees. Linkage analysis revealed that all chromosomes exhibit heterochiasmy, i.e. male- and female restricted meiotic recombination intervals (MRR/FRR). We show that FRR/MRR intervals differ in nucleotide diversity and repeat class content and that this is true also for other Pleuronectidae species. We further show that remnants of a Gypsy-like transposable element insertion on chr13 promotes early male specific expression of gonadal somatic cell derived factor (gsdf). Less than 4 MYA, this male-determining element evolved on an autosomal FRR segment featuring pre-existing male meiotic recombination barriers, thereby creating a Y chromosome. We propose that heterochiasmy may facilitate the evolution of genetic sex determination systems.

genomics↗