Child with De Novo t(1;6)(p22.1;p22.1) translocation and features of ectodermal dysplasia with hypodontia and developmental delay

The Role of the Major Histocompatibility Complex Region on Chromosome 6 in Skin Atrophy: A Mendelian Randomization Study

BACKGROUND

Skin atrophy (SA) is a pathological condition marked by the thinning of the skin, decreased elasticity, and reduced functionality, often arising from aging, chronic glucocorticoid use, or autoimmune diseases.

OBJECTIVE

This study investigates the role of the major histocompatibility complex (MHC) region on chromosome 6 in the development of SA.

METHODS

We applied summary-data-based Mendelian randomization (SMR) using eQTL data of three skin-related tissues (whole blood, lower leg, and suprapubic) from the GTEx database, and SA genome-wide association study data from FinnGen. Further, we conducted functional enrichment, colocalization, and drug enrichment analyses on the core genes (intersection genes) to explore their functions and druggability.

RESULTS

Six core genes (PSORS1C3, HLA-C, HLA-DRB5, HLA-DRB6, HLA-DQA1, and HLA-DQB1) located on chromosome 6p21 were consistently identified across all tissues. Functional enrichment, pathway, and protein-protein interaction analyses revealed that these genes are involved in antigen processing and immune response regulation. Drug enrichment analysis highlighted potential therapeutic targets, including interactions with palladium, azathioprine, and insulin. However, limitations in available data for PSORS1C3 and HLA-DRB6, as well as inconclusive colocalization results, suggest a need for further research.

CONCLUSION

This study highlights the involvement of six core genes within the MHC region on chromosome 6 in the development of SA, emphasizing their roles in immune regulation and antigen presentation. These findings open new avenues for understanding SA and offer a foundation for future investigations into immune-related pathways in skin diseases.

A new variant of the ectodysplasin A receptor death domain gene associated with anhidrotic ectodermal dysplasia in a Turkish family and its simple diagnosis by restriction fragment length polymorphism

Ectodermal dysplasia (ED), which exhibits a wide range of clinical symptoms, may be classified into three major types: hypohidrotic, anhidrotic, and hidrotic. A male child (proband) showing anhidrotic dysplasia was used as the subject of this study. The biopsy of the big toe revealed that the male child had no sweat glands. Genetic analysis of the patient revealed a mutation caused by a homozygous nucleotide substitution in the EDAR-associated death domain (EDARADD) (rs114632254) gene c.439G>A (p.Gly147Arg). Phenotypically, his teeth were sharp, but eight teeth were missing (oligodontia). The patient had normal nails with dry skin, sparse hair, everted lower lip vermilion, hyperpigmented eyelids, and abnormal nasal bridge morphology around the eyes. There is also a homozygous dominant (healthy) female and a heterozygous male in this family, who are cousins (aunt children) to the heterozygous parents. The daughter of the patient was also heterozygous. This mutation represents homozygous recessive inheritance, which we describe for the first time. Furthermore, we demonstrated that this genetic disorder can be readily diagnosed using the restriction fragment length polymorphism (RFLP) method after digestion with MnII restriction endonuclease.

Identification of ectodysplasin-A receptor gene deletion at 2q12.2 and a potential autosomal MR locus

Mental retardation (MR) is not a common feature observed in patients with classical ectodermal dysplasias (EDs). Several genes responsible for EDs and MR have been identified. However, the causation has yet to be identified in a significant number of patients with either ED or MR. Here, we have molecularly characterized a de novo balanced translocation t(1;6)(p22.1;p22.1) in a female patient who had mild features of ED with hypodontia, microcephaly, and cognitive impairment. Mapping of the translocation breakpoints in the patient revealed no obvious causative gene for either ED or MR. Whole genome array CGH analysis unveiled two novel submicroscopic deletions at 2q12.2 and 6q22.3, unrelated to the translocation in the patient. The 2q12.2 deletion contains a known ED gene, ectodysplasin-A receptor (EDAR), and the loss of one copy of this gene is considered to be responsible for the ectodermal phenotype in the patient. It is plausible that a potential autosomal MR gene deleted at 2q12.2 or 6q22.3 is likely the cause of the neurodevelopmental defects in the patient.