Molecular characterization of YY1 allele-specific expression patterns in females diagnosed with Gabriele-de Vries syndrome

• Grant number: 25/04380-0
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: June 14, 2025
• End date: August 01, 2025
• Field of knowledge: Biological Sciences - Genetics - Human and Medical Genetics
• Principal Investigator: Ana Cristina Victorino Krepischi
• Grantee: Bianca Mie Sato Kurashima
• Supervisor: Rafael Martins Galupa
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Centre de Biologie Intégrative de Toulouse (CBI Toulouse), France
• Associated to the scholarship: 23/15506-9 - Investigation of the effect of YY1 variants on the pattern of X chromosome inactivation in women, BP.IC

Abstract

X chromosome inactivation (XCI) is an epigenetic process occurring in early stages of embryonic development in female mammals, which randomly silences one of the two X chromosomes to ensure sex dosage compensation. This process is initiated at the X-inactivation center (XIC) of the future inactive X chromosome (Xi), a regulatory locus of the X chromosome. The XIC contains several non-coding RNA genes, including the XIST gene, whose transcripts coat the Xi and trigger progressive heterochromatinization through epigenetic modifications. The YY1 protein plays a multifaceted role in this process: it activates XIST transcription and mediates the anchoring of XIST transcripts to Xi chromatin, potentially recruiting chromatin-repressive complexes to establish silencing. As a result, females develop two cellular subpopulations, each expressing either maternal or paternal X chromosome. The proportions of these two populations vary across different women and their tissues, ranging from balanced inactivation (~50:50) to fully skewed/exclusive inactivation of one X (0:100). Previously, our research group identified a de novo pathogenic variant in the YY1 gene (cause of Gabriele-de Vries syndrome) in a woman with complete XCI skewing. In light of this context, the present study aims to explore the hypothesis that YY1 mutations influence XCI patterns in females with Gabriele-de Vries syndrome. To test this hypothesis, in the current undergraduate research project, we analyzed the XCI pattern in three novel cases of Gabriele-de Vries syndrome, and detailed their phenotypes. The patients exhibited several clinical features already described in the literature for the syndrome, but with notable clinical heterogeneity. A slight XCI skewing was detected in blood samples of all three patients. This BEPE (2-month period) is proposed to address a central question: Is there differential expression of YY1 and XIST alleles in female patients with Gabriele-de Vries syndrome? To explore this in depth, the internship will take place in Toulouse, France under the supervision of Dr. Rafael Galupa, an expert in the field of XCI. The specific objectives of this research include: (a) training in allele-specific expression analysis by RT-qPCR; (b) acquisition of qualitative and quantitative data on the expression levels of YY1 mutations of two cases of Gabriele-de Vries syndrome - if possible, other X-linked genes will be included in the expression analysis; and (c) training in RNA-FISH, aiming to evaluate YY1 and XIST expression in situ in future studies. By integrating genetic and epigenetic analyses, this work seeks to elucidate how variants in XCI-associated genes can modulate the inactivation pattern, offering insights into their potential role in Gabriele-de Vries syndrome.