A Recurrent Splice Variant Sheds Light on 11β-Hydroxylase Deficiency in a Unique Large Cohort.

Area of Science:

• Endocrinology
• Genetics
• Molecular Biology

Background:

• Congenital adrenal hyperplasia (CAH) can result from 11β-hydroxylase deficiency (11βOHD).
• While sporadic cases are common, comprehensive molecular data for 11βOHD populations are often limited.

Purpose of the Study:

• To characterize the genetic landscape of 11βOHD in a specific cohort.
• To identify and functionally validate a novel, recurrent splice variant in the CYP11B1 gene.

Main Methods:

• CYP11B1 gene sequencing was performed on 250 patients diagnosed with 11βOHD between 1990 and 2024.
• A deep intronic variant (NM_000497.4(CYP11B1):c.954+148C>G) was identified and functionally assessed using in silico analysis and a Minigene Reporter Assay.
• Genotype-phenotype correlations were analyzed, comparing patients with the novel variant to those with severe mutations.

Main Results:

• The c.954+148C>G variant was found to be recurrent, present in 44 patients.
• Functional studies confirmed that this variant disrupts normal splicing by activating a cryptic donor splice site.
• Patients with the c.954+148C>G variant exhibited significantly lower steroid precursor levels and a delayed pubertal onset compared to carriers of severe variants.

Conclusions:

• The study provides extensive genetic data for an 11βOHD cohort, identifying c.954+148C>G as the most frequent variant in the studied Caucasian population.
• The findings highlight the importance of screening deep intronic regions for diagnostic variants.
• Integrating in vitro functional assays with genetic screening is crucial to prevent diagnostic omissions in 11βOHD.