Triple-A Syndrome in Morocco: Founder Effect, Age Estimation of the AAAS c.1331+1G>A Variant, and Implications for Genetic Diagnosis

Introduction

Triple-A syndrome (Triple-A) is an autosomal recessive disorder characterized by alacrimia, achalasia, and adrenal insufficiency. Several variants on the AAAS gene have been described, and some variants are clustered in particular geographical areas, such as the c.1331+1G>A variant which is very frequent in North Africa. Here, we describe the genetic features of Triple-A in a series of unrelated families from Morocco.

Methods

Screening for the AAAS c.1331+1G>A variant was performed by direct sequencing or by PCR-RFLP. Haplotype analysis using Single Tandem Repeat (STR) markers flanking AAAS gene was performed in order to evaluate the founder effect and estimate the age of the c.1331+1G>A variant.

Results

Seven unrelated families with ten individuals clinically diagnosed with Triple-A were evaluated for sequence variations in the AAAS gene. The median age at diagnosis was 3 years, with a range between 2 and 11 years. Molecular analysis revealed that all patients were homozygous for the c.1331+1G>A variant. This variant was not found in 200 healthy controls, indicating that carriers are very rare in the general Moroccan population. Subsequently, STR marker analysis revealed a founder effect and that the most recent common ancestor of Triple-A patients in Morocco would have lived 125 years ago.

Conclusion

This is the largest series of Triple-A in Morocco. The same AAAS c.1331+1G>A variant was found in all patients, suggesting a founder effect in Morocco which was subsequently confirmed by microsatellite marker analysis. Therefore, this variant should be systematically investigated to diagnose Triple-A in Morocco.

A novel variant in BMPR1B causes acromesomelic dysplasia Grebe type in a consanguineous Moroccan family: Expanding the phenotypic and mutational spectrum of acromesomelic dysplasias

Acromesomelic dysplasia Grebe type (AMD Grebe type) is an autosomal recessive trait characterized by short stature, shortened limbs and malformations of the hands and feet. It is caused by variants in the growth differentiation factor 5 (GDF5) or, in rare cases, its receptor, the bone morphogenetic protein receptor-1B (BMPR1B). Here, we report a novel homozygous BMPR1B variant causing AMD Grebe type in a consanguineous Moroccan family with two affected sibs from BRO Biobank. Remarkably, the affected individuals showed additional features including bilateral simian creases, lumbar hyperlordosis, as well as lower limb length inequality and dislocated hips in one of them, which were never reported previously for AMD Grebe type patients. The identified novel BMPR1B variant (c.1201C>T, p.R401*) is predicted to result in loss of function of the BMPR1B protein either by nonsense-mediated mRNA decay or production of a truncated BMPR1B protein. Thus, these findings expand the phenotypic and mutational spectrum of AMD, and may improve the diagnosis of AMD and enable appropriate genetic counselling to be offered to patients.

Molecular heterogeneity of β-thalassemia variants in the Eastern region of Morocco

Background

β‐thalassemia syndromes are the most common hereditary blood disorders in the world and are recognized as a major health problem in Morocco. They are characterized by the reduction or the absence of β‐globin chain synthesis. The severity of the disease depends on the nature of the variants affecting the β‐globin gene (HBB), and each ethnic group has its own mutation spectrum. Hereby, we present, for the first time, the molecular profile of β‐thalassemia in the Eastern region of Morocco.

Methods

This study concerns 39 cases from 33 families who were enrolled in the BRO Biobank. Nineteen were diagnosed with β‐thalassemia major and 20 with β‐thalassemia minor. To detect mutations of the β‐globin gene, we have used RFLP‐PCR and Sanger sequencing.

Results

Nine known β‐thalassemia variants have been identified. Among these, we reported, for the first time in the Moroccan population, the Czechoslovakian variant C38/39(‐C) at homozygous state. The C39(C > T) was the most frequent variant (72.54%), followed by FSC5(‐CT) (5.88%), FSC6(−A), IVS‐1‐110(G > A), −29(A > G), C38/39(‐C) (3.92% each), and finally by IVS‐I‐1(G > A), IVS‐II‐1(G > A), and −56(G > C) (1.96%). Of particular interest this mutational spectrum of β‐thalassemia is very different from that found in previous studies in Morocco or in other North African countries.

Conclusion

This study is the first contribution to the description of the molecular profile of β‐thalassemia in the Eastern region of Morocco. It shows the high molecular heterogeneity of β‐thalassemia in our country. Therefore, these results can be valuable for the implementation of carrier screening, genetic counseling, and prenatal diagnosis programs.