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bioRxiv · 10.1101/2023.04.26.538436

Incomplete dosage balance and dosage compensation in the ZZ/ZW Gila monster (Heloderma suspectum) revealed by de novo genome assembly

Webster, T. H.·Vannan, A.·Pinto, B. J.·Denbrock, G.·Morales, M.·Dolby, G. A.·Fiddes, I. T.·DeNardo, D. F.·Wilson, M. A.
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Abstract

Reptiles exhibit a variety of modes of sex determination, including both temperature-dependent and genetic mechanisms. Among those species with genetic sex determination, sex chromosomes of varying heterogamety (XX/XY and ZZ/ZW) have been observed with different degrees of differentiation. Karyotype studies have demonstrated that Gila monsters (Heloderma suspectum) have ZZ/ZW sex determination and this system is likely homologous to the ZZ/ZW system in the Komodo dragon (Varanus komodoensis), but little else is known about their sex chromosomes. Here, we report the assembly and analysis of the Gila monster genome. We generated a de novo draft genome assembly for a male using 10X Genomics technology. We further generated and analyzed short-read whole genome sequencing and whole transcriptome sequencing data for three males and three females. By comparing female and male genomic data, we identified four putative Z-chromosome scaffolds. These putative Z-chromosome scaffolds are homologous to Z-linked scaffolds identified in the Komodo dragon. Further, by analyzing RNAseq data, we observed evidence of incomplete dosage compensation between the Gila monster Z chromosome and autosomes and a lack of balance in Z-linked expression between the sexes. In particular, we observe lower expression of the Z in females (ZW) than males (ZZ) on a global basis, though we find evidence suggesting local gene-by-gene compensation. This pattern has been observed in most other ZZ/ZW systems studied to date and may represent a general pattern for female heterogamety in vertebrates.

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Webster, T. H., Vannan, A., Pinto, B. J., Denbrock, G., Morales, M., Dolby, G. A., Fiddes, I. T., DeNardo, D. F., Wilson, M. A.. 2023-04-28. Incomplete dosage balance and dosage compensation in the ZZ/ZW Gila monster (Heloderma suspectum) revealed by de novo genome assembly. https://doi.org/10.1101/2023.04.26.538436

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