8703 Retrotranscribed sequences, a missing piece in the puzzle of Differences/Disorders of Sex Development with unknown genetic causes
Authors: Batista Rafael Loch , Da Roz D’Alessandre Nathália , Rego Fernanda Orpinelli , Guardia Gabriela Der Agopian , Braga Barbara Leitao , Nishi Mirian Yumie , Domenice Sorahia , Mendonca Berenice Bilharinho , Galante Pedro Alexandre Favoretto 
Published: October 2024

Abstract
Disclosure: R.L. Batista: None. N.D. D’Alessandre: None. F.O. Rego: None. G.D. Guardia: None. B. Leitao Braga: None. M.Y. Nishi: None. S. Domenice: None. B.B. Mendonca: None. P.A. Galante: None.
Background: The human genome is a complex and dynamic structure. These two characteristics have a major contribution from the Mobile Elements (MEs), which comprise at least 50% of the human genome and are sources of genetic novelties. LINE1 (L1), Alu elements, SVA, and LTR elements (HERVs) are MEs highly frequent in the human genome. MEs can create genomic structural variations with consequent roles in health and diseases. Differences of sex development (DSD) are a heterogeneous group of congenital conditions that result in discordance between an individual’s sex chromosomes, gonads, or anatomic sex. DSDs are caused by genomic variations in genes involved in gonadal or genital development.Objective: We comprehensively examine the potential contributions of MEs as a source of genetic novelties in genes related to sexual development and in the etiology of 46,XY DSD. Subjects and methods: First, we investigate the potential role of fixed MEs, including L1, Alu elements, and retroCNVs, present in DSD genes using whole exome sequencing (WES) data. By applying bioinformatics tools and appropriate pipelines, we parallelly analyzed local WES data from 443 individuals from our lab and a public database (GnomAD). Second, we seek unfixed (polymorphic or somatically acquired) MEs in WES data from a cohort of 41 unrelated DSD patients with undetermined molecular etiology. We found 2,408 L1 elements, 3,587 Alu elements, and 14 SVAs inserted in 75 out of 81 DSD-related genes (92.6%) of the DSD genes. When examining by element class, we identified 3,587 fixed Alus that affected over 70 DSD genes, resulting in an average of approximately 47 Alu element insertions per gene. For L1 elements, 2,408 fixed elements were found in about 60 genes (∼37 insertions per gene). Subsequently, the number of fixed elements identified in SVAs (n=14) and HERVKs (n=8) decreased significantly. Among these insertions, seven genes were identified harboring one retrocopy each and four genes with two or more retrocopies each. In total, we found 19 retrocopies in 11 DSD genes. That massive presence of mobile elements in DSD genes may suggest an evolutionary contribution of MEs incorporation through evolution in human sexual development.Regarding non-fixed elements, we found two polymorphic events: an L1 insertion into WT1 and an Alu insertion into GTF2F1, two key genes to the DSD development. We also found an L1 insertion in the DNAH2 gene (related to spermatogenic failure and male infertility) and an Alu insertion in the TEX15 gene (related to male infertility in mice). Interestingly, we also identified one somatically acquired retroCNV event in a non-classical DSD gene (CHST8). In summary, our study underscores the significance of MEs as potential sources of genetic innovation in human sexual development and as molecular etiologies of DSD.
Presentation: 6/1/2024