Linkage disequilibrium in inbred North African families allows fine genetic and physical mapping of triple A syndrome

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.

Triple A syndrome (Allgrove syndrome): improving outcomes with a multidisciplinary approach

Allgrove syndrome or triple A (3A) syndrome is a multisystem disorder which classically involves the triad of esophageal achalasia, alacrima, and adrenal insufficiency due to adrenocorticotropin hormone insensitivity. It follows an autosomal recessive pattern of inheritance and is associated with mutations in the AAAS (achalasia–addisonianism–alacrima syndrome) gene. Since its first description in 1978, the knowledge on clinical and genetic characteristics has been expanding; however, the current literature is limited to case reports and case reviews. Early recognition of the syndrome is challenging, given the rarity of the condition and high phenotypic heterogeneity even among members of kin. The coordination of care for these patients requires a multidisciplinary team of specialists, including endocrinologists, neurologists, gastroenterologists, ophthalmologists, developmental specialists, dentists, geneticists, and surgeons. In this review, we aim to summarize the current recommendations for the diagnosis, management, and follow-up of patients with 3A syndrome.

A Tunisian patient with two rare syndromes: triple a syndrome and congenital hypogonadotropic hypogonadism

BACKGROUND/AIMS

The coexistence of triple A syndrome (AAAS) and congenital hypogonadotropic hypogonadism (CHH) has so far not been reported in the literature. This study aimed to characterize at the clinical and genetic level one patient presenting an association of AAAS and CHH in order to identify causal mutations.

METHODS

Clinical and endocrinal investigations were performed and followed by mutational screening of candidate genes.

RESULTS

At the age of 18, the patient presented sexual infantilism, a micropenis and gynecomastia. No mutation was revealed in GnRHR, TACR3/TAC3, PROK2/PROKR2 and PROP1 genes, except a homozygous intronic variation (c.244 + 128C>T; dbSNP: rs350129) in the KISS1R gene, which is likely nondeleterious. A homozygous splice-donor site mutation (IVS14 + 1G>A) was found in the AAAS gene. This mutation, responsible for AAAS, is a founder mutation in North Africa.

CONCLUSION

This is the first report on a Tunisian patient with the coexistence of AAAS and CHH. The diagnosis of CHH should be taken in consideration in patients with Allgrove syndrome and who carry the IVS14 + 1G>A mutation as this might challenge appropriate genetic counseling.

[Allgrove syndrome. Report on a family]

Triple A or Allgrove syndrome is a rare autosomal recessive disease with alacrima, achalasia, and ACTH-resistant adrenal insufficiency. It is usually associated with neurological disorders. Recently, mutations in the AAAS, a candidate gene mapped to chromosome 12q13, were identified. We report a family with seven affected siblings. All of them have signs of alacrima, four were operated on for achalasia, five have neurological abnormalities including cranial nerve abnormalities, amyotrophic lateral sclerosis, pyramidal syndrome, distal motor neuropathy, and amyotrophy, and two have adrenal insufficiency. Triple A syndrome should be considered in any young patient with alacrima.

Triple-A syndrome--the first Chinese patient with novel mutations in the AAAS gene

We report on the first Chinese patient with triple-A syndrome, who presented at 22 months with status epilepticus secondary to hyponatraemia and hypoglycaemia. Subsequent endocrine investigations confirmed primary adrenal insufficiency and aldosterone deficiency. In the presence of achalasia and alacrima, this patient satisfies the diagnostic criteria of triple-A syndrome. Further molecular testing detected compound heterozygous mutations in the AAAS gene: a c.580C --> T transition in exon 7 and a c.771delG single nucleotide deletion in exon 8. Testing of parents and brother confirmed their heterozygous carrier status.

Mice lacking the nuclear pore complex protein ALADIN show female infertility but fail to develop a phenotype resembling human triple A syndrome

Triple A syndrome is a human autosomal recessive disorder characterized by adrenal insufficiency, achalasia, alacrima, and neurological abnormalities affecting the central, peripheral, and autonomic nervous systems. In humans, this disease is caused by mutations in the AAAS gene, which encodes ALADIN, a protein that belongs to the family of WD-repeat proteins and localizes to nuclear pore complexes. To analyze the function of the gene in the context of the whole organism and in an attempt to obtain an animal model for human triple A syndrome, we generated mice lacking a functional Aaas gene. The Aaas-/- animals were found to be externally indistinguishable from their wild-type littermates, although their body weight was on the average lower than that of wild-type mice. Histological analysis of various tissues failed to reveal any differences between Aaas-/- and wild-type mice. Aaas-/- mice exhibit unexpectedly mild abnormal behavior and only minor neurological deficits. Our data show that the lack of ALADIN in mice does not lead to a triple A syndrome-like disease. Thus, in mice either the function of ALADIN differs from that in humans, its loss can be readily compensated for, or additional factors, such as environmental conditions or genetic modifiers, contribute to the disease.

Achalasia of the cardia in Allgrove's (triple A) syndrome: histopathologic study of 10 cases

Allgrove's syndrome, i.e., achalasia, addisonianism, alacrima (OMIM 231550) is an autosomal recessive disorder recently associated with the AAAS gene coding for the Aladin protein. However, the pathophysiology of achalasia in Allgrove's syndrome remains obscure. Here we investigated the histopathology of the cardia in Allgrove's syndrome. Myectomy specimens from 10 children with Allgrove's syndrome and four normal cardia were studied by routine staining and by immunohistochemistry for the pan-neuronal marker PGP9.5, neuronal NO synthase, interstitial cells of Cajal, and CD3+ lymphocytes. In the normal cardia, myenteric ganglia, intramuscular nerve fibers, and interstitial cells of Cajal were numerous, whereas myenteric fibrosis and lymphocyte infiltrates were absent. In Allgrove's syndrome, fibrosis of the intermuscular plane was prevalent in all patients. Myenteric ganglia were absent, decreased, or apparently normal in 1 of 10, 8 of 10, and 1 of 10, respectively. Neuronal NO synthase was absent in 7 of 10 and decreased in 3 of 10, whereas interstitial cells of Cajal appeared normal in 7 of 10 and decreased in 3 of 10. Lymphocytes infiltrating the myenteric plexus were present in 6 of 10. Pyloromyectomy specimens available for six patients showed normal histopathologic features. In conclusion, the lack of neuronal NO synthase and fibrosis of the intermuscular plane can be linked to the defective cardia relaxation. Other features were less constant and may reflect the variability of disease expression and progression among patients with Allgrove's syndrome.

Chromosomal fragility in patients with triple A syndrome

Triple A syndrome is a rare, autosomal recessive disorder characterized by alacrima, achalasia, and adrenal insufficiency. Previous studies have shown that the triple A gene (AAAS) maps to chromosomal band 12q13. Mutations in the AAAS gene have been identified in triple A syndrome patients; however, the function of this gene is still obscure. We used classical and high-resolution chromosome analyses along with chromosome painting and DNA sequencing to study patients with triple A syndrome. We observed abnormalities in the heterochromatic region of chromosome 9 that included chromatid breaks, chromosome breaks, whole chromosome arm loss, and marker chromosomes, which occurred at unusually high frequencies in affected patients and heterozygotes. Our study raises the possibility of an association between chromosomal fragility in band 9q12 and triple A syndrome. Further investigation is necessary to understand the biologic basis of this finding in the context of triple A syndrome.

New insights into the molecular basis of the triple A syndrome

The triple A syndrome (MIM*231550) is a rare autosomal recessive disorder characterized by adrenocorticotropic hormone (ACTH) resistant adrenal failure, achalasia, alacrima and a variety of neurological and dermatological features. Adrenal insufficiency usually presents in the first decade of life, however in some patients it may occur later in life or may even lack completely. Recently, we and others identified a novel gene on chromosome 12q13, designated AAAS (Achalasia-Addisonianism-Alacrima-Syndrome gene) which is mutated in patients with triple A syndrome. We investigated n=84 families including 111 patients with clinically suggested triple A syndrome and identified homozygous or compound heterozygous AAAS mutations in 78 families. Genotype/phenotype analyses revealed a highly variable occurrence, age of onset and severity of all clinical symptoms between patients with the same AAAS mutation. The obvious lack of a genotype/phenotype relationship is suggestive of modifying genes/factors which need to be determined. The AAAS protein function is unknown. With four WD repeats it belongs to the family of WD repeat-containing proteins which may exhibit a high degree of functional diversity. The subcellular localization of the protein and the determination of its putative binding partners will shed light on the role of the AAAS protein for the development and function of the adrenal gland and other neuroendocrine structures.

Mutant WD-repeat protein in triple-A syndrome

Triple-A syndrome (MIM 231550; also known as Allgrove syndrome) is an autosomal recessive disorder characterized by adrenocorticotropin hormone (ACTH)-resistant adrenal insufficiency, achalasia of the oesophageal cardia and alacrima. Whereas several lines of evidence indicate that triple-A syndrome results from the abnormal development of the autonomic nervous system, late-onset progressive neurological symptoms (including cerebellar ataxia, peripheral neuropathy and mild dementia) suggest that the central nervous system may be involved in the disease as well. Using fine-mapping based on linkage disequilibrium in North African inbred families, we identified a short ancestral haplotype on chromosome 12q13 (<1 cM), sequenced a BAC contig encompassing the triple-A minimal region and identified a novel gene (AAAS) encoding a protein of 547 amino acids that is mutant in affected individuals. We found five homozygous truncating mutations in unrelated patients and ascribed the founder effect in North African families to a single splice-donor site mutation that occurred more than 2,400 years ago. The predicted product of AAAS, ALADIN (for alacrima-achalasia-adrenal insufficiency neurologic disorder), belongs to the WD-repeat family of regulatory proteins, indicating a new disease mechanism involved in triple-A syndrome. The expression of the gene in both neuroendocrine and cerebral structures points to a role in the normal development of the peripheral and central nervous systems.