Pathogenic variants in the Dopachrome tautomerase (DCT) gene (NM_001129889.2) have recently been associated with a novel oculocutaneous albinism (OCA) subgroup, type 8 (OCA8). Here, we report the establishment of an induced pluripotent stem cell (iPSC) line, INMi007-A, derived from the skin fibroblasts of an individual compound heterozygous for two pathogenic variants in DCT, using the non-integrative Sendai virus reprogramming method. This iPSC line harbors a single-nucleotide variant in exon 1 of DCT (c.118T > A; p.(Cys40Ser)) and a 14-bp deletion in exon 9 (c.1406_1419del; p.(Phe469*)). This cell line represents an important tool for studying the pathophysiology of OCA8.

Oculocutaneous albinism type 1 is a genetic disorder caused by the disruption of tyrosinase activity in the melanogenesis pathway. The tyrosinase's intramelanosomal domain can be subdivided into the catalytic and Cys-rich subdomains, integral for protein stability and catalytic activity. To understand the movement in the tyrosinase intra-melanosomal subdomains and their link to its catalytic activity, we perform essential dynamics on homology models for tyrosinase and the mutant variants R217Q, R402Q, and R217Q/R402Q. Dimensional reduction techniques, such as principal component analysis (PCA), are fundamental to systematically comprehending collective movements in protein structure. The alpha-carbon atomic coordinates for all residues across a 100-ns molecular dynamics trajectory were input into the PCA function, and the results were analyzed alongside correlated movements and free energy profiles for each protein structure. The PCA-identified coordinated movement underlying the stable conformations of wild-type tyrosinase arises within the H9 and H10 helices, which are proximal to the flexible tunnel system and the interface of the catalytic and Cys-rich subdomains. In contrast, genetic mutations R217Q and R217Q/R402Q disrupt the coordinated movement of the tyrosinase intra-melanosomal domain, indicating a cause of mutant variant instability.

Hermansky-Pudlak Syndrome (HPS) type 1 (HPS-1) is an autosomal recessive disorder characterized by oculocutaneous albinism, platelet dysfunction, and pulmonary fibrosis (HPS-PF), the leading cause of mortality in these patients. HPS-PF manifests earlier than idiopathic pulmonary fibrosis, typically between 30 and 40 years of age. The etiology and drivers of HPS-PF progression remain poorly understood, and no FDA-approved therapies exist. Neutrophil extracellular traps (NETs) and neutrophil-derived mediators have emerged as key players in fibrosis, promoting lung injury, inflammation, and fibroblast activation. This study evaluates the role of neutrophil activation in age-related changes in patients with HPS-1, focusing on differences in inflammatory markers, neutrophil granules, and NETosis capacity. We observed significantly elevated levels of NETs, neutrophil granule proteins (NE, NGAL, LF), and inflammatory cytokines (IL-8, IL-6) in patients with HPS-1 older than 40 years compared to younger patients and healthy controls. Additionally, fibrosis-related markers (MMP-7 and MMP-8) were significantly higher in older patients. Elevated levels of anandamide (AEA), a circulating marker of HPS-PF, were positively associated with neutrophil granule markers in older patients, suggesting its association with fibrosis. Neutrophils from older patients also demonstrated increased NETosis capacity. These findings suggest that age-related neutrophil activation may contribute to an inflammatory environment that promotes fibrosis progression in HPS-1.

Albinism is a genetic disorder characterized by a defect in melanin biosynthesis. Ophthalmological and dermatological impairments vary according to the patient genotype and are highly heterogenous. Recently, variants in the DCT gene were showed to be responsible for a new type of oculocutaneous albinism (OCA) named OCA8. We report the ophthalmological, electrophysiological, and dermatological characteristics of three patients with genetically confirmed OCA8. This is a retrospective study of three patients with OCA8. Complete dermatological, ophthalmological, and orthoptic examinations were performed with clinical exploration and multimodal imaging. Visual evoked potentials (VEPs) were performed to characterize chiasmal decussation in two of the three patients. The dermatological phenotype was mild, whereas all three patients exhibited infantile nystagmus syndrome with reduced visual acuity, foveal hypoplasia (grade 3), macular hypopigmentation (graded from 2 to 1), and iris transillumination (grade 3). Patients who could undergo a VEP examination exhibited signs of strong chiasmal misrouting. Recently, pathogenic variants in the DCT gene were proven to cause OCA. Whereas patients with OCA8 exhibit a milder dermatological phenotype than others, their vision was initially described as impaired. The present report confirms previous findings and suggests that chiasmal misrouting is present in OCA8. This, together with recent findings in the murine model, supports the hypothesis that DCT regulates levels of L-Dopa and downstream signaling in the developing retina. These results convey critical future therapeutic implications.

Oculocutaneous albinism type 2 (OCA-2, OMIM: 203200) is associated with variants in the OCA2 gene. In this study, we aimed to re-classify variants of uncertain significance (VUS) in OCA2 by evaluating subcellular localization and channel activity through multiplex assays of variant effect (MAVEs). Following the ClinGen guidelines for PS3 evidence, we selected 13 OCA2 variants from ClinVar (6 benign/likely benign [B/LB] and 7 pathogenic/likely pathogenic [P/LP]) for OddsPath analysis. The P/LP variants exhibited abnormal functions, while the B/LB variants demonstrated normal functions, supporting the application of "PS3_moderate" evidence for VUS re-classification. In our functional evaluation of 30 VUS identified in 38 individuals with suspected OCA-2 by trio whole-exome sequencing, we observed 6 VUS with abnormal localization and 11 with abnormal channel activity. Based on PS3_moderate evidence, 8 VUS were re-classified as LP, while 22 remained VUS. Consequently, 7 out of 38 previously undiagnosed patients received a molecular diagnosis of OCA-2. These MAVEs offer a robust approach for curating OCA2 VUS, enhancing diagnostic accuracy, and informing genetic counseling. Additionally, this variant cohort is a valuable resource for public databases.