Hidradenitis suppurativa (HS) is a chronic skin disease characterized by painful, recurrent abscesses, nodules, and scarring, primarily in skin folds. The exact causes of HS are multifactorial, involving genetic, hormonal, and environmental factors. It is associated with systemic diseases like metabolic syndrome and inflammatory bowel disease. Genetic studies have identified mutations in the γ-secretase complex, which affects Notch signaling pathways critical for skin cell regulation. Despite its high heritability, most HS reported cases do not follow a simple genetic pattern. In this article, we performed a whole-exome sequencing (WES) on a cohort of 100 individuals with HS and we provide a comprehensive review of the variants known to be described or associated with HS, referencing 91 of them in the γ-secretase and 78 in other genes involved in the Notch pathway, keratinization, or immune response. From this new genetic analysis, we add ten new variants to these catalogs.

Nicastrin (NICT) is a transmembrane protein physically associated with the polytypical aspartyl protease presenilin that plays a vital role in the correct localization and stabilization of presenilin to the membrane-bound γ-secretase complex. This complex is involved in the regulation of a wide range of cellular events including cell signaling and the regulation of endocytosed membrane proteins for their trafficking and protein processing. Mehtods: In Trypanosoma cruzi, the causal agent of the Chagas disease, an NICT-like protein (Tc/NICT) was identified with a short C-terminus orthologous to the human protein, a large ectodomain (ECD) with numerous glycosylation sites and a single core transmembrane domain containing a putative TM-domain (457GSVGA461) important for the γ-secretase complex activity. Results: Using the Spot-synthesis strategy with Chagasic patient sera, five extracellular epitopes were identified and synthetic forms were used to generate rabbit anti-Tc/NICT polyclonal serum that recognized a ~72-kDa molecule in immunoblots of T. cruzi epimastigote extracts. Confocal microscopy suggests that Tc/NICT is localized in the flagellar pocket, which is consistent with data from our previous studies with a T. cruzi presenilin-like protein. Phylogenetically, Tc/NICT was localized within a subgroup with the T. rangeli protein that are clearly detached from the other Trypanosomatidae such as T. brucei. These results, together with a comparative analysis of the selected peptide sequence regions between the T. cruzi and mammalian proteins suggest a divergence from the human NICT that might be relevant to Chagas disease pathology. As a whole, our data show that an NICT-like protein is expressed in the infective and replicative stages of T. cruzi and may be considered further evidence for a γ-secretase complex in trypanosomatids.