Arab founder variants: Contributions to clinical genomics and precision medicine

Bi-allelic UGGT1 variants cause a congenital disorder of glycosylation

Congenital disorders of glycosylation (CDGs) comprise a large heterogeneous group of metabolic conditions caused by defects in glycoprotein and glycolipid glycan assembly and remodeling, a fundamental molecular process with wide-ranging biological roles. Herein, we describe bi-allelic UGGT1 variants in fifteen individuals from ten unrelated families of various ethnic backgrounds as a cause of a distinctive CDG of variable severity. The cardinal clinical features of UGGT1-CDG involve developmental delay, intellectual disability, seizures, characteristic facial features, and microcephaly in the majority (9/11 affected individuals for whom measurements were available). The more severely affected individuals display congenital heart malformations, variable skeletal abnormalities including scoliosis, and hepatic and renal involvement, including polycystic kidneys mimicking autosomal recessive polycystic kidney disease. Clinical studies defined genotype-phenotype correlations, showing bi-allelic UGGT1 loss-of-function variants associated with increased disease severity, including death in infancy. UGGT1 encodes UDP-glucose:glycoprotein glucosyltransferase 1, an enzyme critical for maintaining quality control of N-linked glycosylation. Molecular studies showed that pathogenic UGGT1 variants impair UGGT1 glucosylation and catalytic activity, disrupt mRNA splicing, or inhibit endoplasmic reticulum (ER) retention. Collectively, our data provide a comprehensive genetic, clinical, and molecular characterization of UGGT1-CDG, broadening the spectrum of N-linked glycosylation disorders.

Genomics of rare diseases in the Greater Middle East

The Greater Middle East (GME) represents a concentrated region of unparalleled genetic diversity, characterized by an abundance of distinct alleles, founder mutations and extensive autozygosity driven by high consanguinity rates. These genetic hallmarks present a unique, yet vastly untapped resource for genomic research on Mendelian diseases. Despite this immense potential, the GME continues to face substantial challenges in comprehensive data collection and analysis. This Perspective highlights the region's unique position as a natural laboratory for genetic discovery and explores the challenges that have stifled progress thus far. Importantly, we propose strategic solutions, advocating for an all-inclusive research approach. With targeted investment and focused efforts, the latent genetic wealth in the GME can be transformed into a global hub for genomic research that will redefine and advance our understanding of the human genome.