9378 Knockdown Of The Cdh2 Gene In Zebrafish Determines Its Role In Terminal Hormone Differentiation

Abstract Disclosure: B.V. Fernandes: None. C. MacRae: None. L.R. Carvalho: None. M. Junqueira: None. Introduction: Congenital hypopituitarism (CH) is characterized by the deficiency of one or more pituitary hormones. Whole exome sequencing (WES) has allowed the identification of novel/rare variants in genetic diseases. Among CH patients, 85% lack a molecular diagnosis. WES approach in a patients born to consanguineous parents identified the homozygous variant (c.865G>A, p. Val289Ile) in the CDH2 gene that produce N-Cadherin protein responsible for cell-cell adhesion. This variant was predicted as likely pathogenic allelic variant by ACMG criteria was found in a patient with GH, TSH, ACTH, LF/FSH deficiencies associated with an ectopic neurohypophysis and pituitary hypoplasia. CDH2 analysis in a cohort of 219 patients with CH, followed in a single Brazilian center, identified 3 unrelated families with heterozygous variants and incomplete penetrance where 2 were novel, in addition to the p. Val289Ile. The deleterious effect of the homozygous variant on cell adhesion properties was confirmed in permanent transfection assays in L1 fibroblast cell lines. To determine the role of the cdh2 gene in pituitary development and hormone production and secretion, we selected zebrafish as an animal model due to its 75% genetic homology with humans. Knockout of cdh2 using Crispr/cas9 genomic edition resulted in 85% lethality of animals at 48 hours post-fertilization (hpf), precluding analysis of its role during pituitary development. Objective: To produce a cdh2 knockdown in zebrafish for phenotypic and molecular analysis. Materials and Methods: The pET28B-RfxCas13d-His plasmid was transformed, linearized, and followed by in vitro transcription to produce Cas13 mRNA. Three guide RNAs targeting the cdh2 gene were designed to guide Cas13 to the target. The Cas13/RNA guide complex was injected into single-cell embryos, and phenotypic analyses were performed under a stereomicroscope until 96 hpf. To evaluate cdh2, prop1, pit1 and gh gene expression by RT-PCR, embryos were collected at 24, 48, 72, and 96 hpf. Results: Knockdown animals exhibited microcephaly, cardiac edema, and microphthalmia during embryonic development. CDH2 expression was decreased by 75% in the first 24 hours of life and began to recover by 48 hours, gradually increasing until 96 hpf when it equaled to WT. gh expression was statistically decreased at 48h compared to WT, with an increased gh expression similar to cdh2 increasing reaching similar WT levels by 96 hpf. There was no statistically significant difference in prop1 and pit1 expression compared to WT in the analyzed periods. Conclusion: The cdh2 knockdown in zebrafish using Cas13 enzyme was effective with cdh2 decreased expression by 75% presenting a phenotype similar to the knockout model. Decreased gh expression at 48h suggests an important role of cdh2 in hormonal terminal differentiation, which should be corroborated by analysis of other hormone expressions. Presentation: 6/2/2024