Mortality-associated immunological abnormalities in trichothiodystrophy: correlation of reduced levels of immunoglobulin and neutrophils with poor patient survival

Impaired B-cell function in ERCC2 deficiency

Background

Trichothiodystrophy-1 (TTD1) is an autosomal-recessive disease and caused by mutations in ERCC2, a gene coding for a subunit of the TFIIH transcription and nucleotide-excision repair (NER) factor. In almost half of these patients infectious susceptibility has been reported but the underlying molecular mechanism leading to immunodeficiency is largely unknown.

Objective

The aim of this study was to perform extended molecular and immunological phenotyping in patients suffering from TTD1.

Methods

Cellular immune phenotype was investigated using multicolor flow cytometry. DNA repair efficiency was evaluated in UV-irradiation assays. Furthermore, early BCR activation events and proliferation of TTD1 lymphocytes following DNA damage induction was tested. In addition, we performed differential gene expression analysis in peripheral lymphocytes of TTD1 patients.

Results

We investigated three unrelated TTD1 patients who presented with recurrent infections early in life of whom two harbored novel ERCC2 mutations and the third patient is a carrier of previously described pathogenic ERCC2 mutations. Hypogammaglobulinemia and decreased antibody responses following vaccination were found. TTD1 B-cells showed accumulation of γ-H2AX levels, decreased proliferation activity and reduced cell viability following UV-irradiation. mRNA sequencing analysis revealed significantly downregulated genes needed for B-cell development and activation. Analysis of B-cell subpopulations showed low numbers of naïve and transitional B-cells in TTD1 patients, indicating abnormal B-cell differentiation in vivo.

Conclusion

In summary, our analyses confirmed the pathogenicity of novel ERCC2 mutations and show that ERCC2 deficiency is associated with antibody deficiency most likely due to altered B-cell differentiation resulting from impaired BCR-mediated B-cell activation and activation-induced gene transcription.

Altered skin microbiome, inflammation, and JAK/STAT signaling in Southeast Asian ichthyosis patients

BACKGROUND

Congenital ichthyosis (CI) is a collective group of rare hereditary skin disorders. Patients present with epidermal scaling, fissuring, chronic inflammation, and increased susceptibility to infections. Recently, there is increased interest in the skin microbiome; therefore, we hypothesized that CI patients likely exhibit an abnormal profile of epidermal microbes because of their various underlying skin barrier defects. Among recruited individuals of Southeast Asian ethnicity, we performed skin meta-genomics (i.e., whole-exome sequencing to capture the entire multi-kingdom profile, including fungi, protists, archaea, bacteria, and viruses), comparing 36 CI patients (representing seven subtypes) with that of 15 CI age-and gender-matched controls who had no family history of CI.

RESULTS

This case-control study revealed 20 novel and 31 recurrent pathogenic variants. Microbiome meta-analysis showed distinct microbial populations, decreases in commensal microbiota, and higher colonization by pathogenic species associated with CI; these were correlated with increased production of inflammatory cytokines and Th17- and JAK/STAT-signaling pathways in peripheral blood mononuclear cells. In the wounds of CI patients, we identified specific changes in microbiota and alterations in inflammatory pathways, which are likely responsible for impaired wound healing.

CONCLUSIONS

Together, this research enhances our understanding of the microbiological, immunological, and molecular properties of CI and should provide critical information for improving therapeutic management of CI patients.

Trichothiodystrophy-associated MPLKIP maintains DBR1 levels for proper lariat debranching and ectodermal differentiation

The brittle hair syndrome Trichothiodystrophy (TTD) is characterized by variable clinical features, including photosensitivity, ichthyosis, growth retardation, microcephaly, intellectual disability, hypogonadism, and anaemia. TTD-associated mutations typically cause unstable mutant proteins involved in various steps of gene expression, severely reducing steady-state mutant protein levels. However, to date, no such link to instability of gene-expression factors for TTD-associated mutations in MPLKIP/TTDN1 has been established. Here, we present seven additional TTD individuals with MPLKIP mutations from five consanguineous families, with a newly identified MPLKIP variant in one family. By mass spectrometry-based interaction proteomics, we demonstrate that MPLKIP interacts with core splicing factors and the lariat debranching protein DBR1. MPLKIP-deficient primary fibroblasts have reduced steady-state DBR1 protein levels. Using Human Skin Equivalents (HSEs), we observed impaired keratinocyte differentiation associated with compromised splicing and eventually, an imbalanced proteome affecting skin development and, interestingly, also the immune system. Our data show that MPLKIP, through its DBR1 stabilizing role, is implicated in mRNA splicing, which is of particular importance in highly differentiated tissue.

Evaluation of immunological abnormalities in patients with rare syndromes

Introduction

Recurrent infections are important problems in syndromic patients. This study aimed to evaluate immunological abnormalities in patients who presented with recurrent infections and were diagnosed with rare syndromes.

Material and methods

This retrospective analysis included 14 patients with complaints of recurrent infections, all of whom were diagnosed with a rare syndrome.

Results

The study group consisted of patients with Aicardi syndrome, Brugada syndrome, Phelan- McDermid syndrome, trichothiodystrophy, LEOPARD syndrome, Prader-Willi syndrome, Seckel syndrome, trisomy 18 (Edwards' syndrome), Wiedemann-Steiner syndrome, West syndrome, Williams syndrome, 47,XYY syndrome, 16p13 deletion syndrome, and 13q1.3 deletion syndrome. Seven patients (50%) were girls and seven (50%) were boys (mean age, 56.7 ±32.9 months; median [range] age: 45.5 [27-153] months). There were high rates of consanguinity (50%), cesarean section delivery (71%), and hospitalization in the intensive care unit (78.5%). No patients had a family history of immunodeficiency. On admission, all patients exhibited humoral and/or cellular immune system abnormalities. During the follow-up period, all T-cell abnormalities were improved after immunoglobulin replacement therapy (IGRT), while B-cell abnormalities persisted. These findings suggested that the patients predominantly had antibody deficiencies associated with mild T-cell abnormalities because of recurrent infections. The rates of infections and hospitalizations were significantly reduced after IGRT (p < 0.001); the rate of intensive care unit admission also significantly decreased (from 78.5% to 21.4%). Two of the three oxygen-dependent patients exhibited improvement therein. IGRT was discontinued in two patients with significant clinical improvement during follow-up.

Conclusions

An immunological evaluation should be considered in pediatric patients with rare syndromes and recurrent infections. IGRT may help to improve the prognoses of these patients.

Reduced levels of prostaglandin I2 synthase: a distinctive feature of the cancer-free trichothiodystrophy

The cancer-free photosensitive trichothiodystrophy (PS-TTD) and the cancer-prone xeroderma pigmentosum (XP) are rare monogenic disorders that can arise from mutations in the same genes, namely ERCC2/XPD or ERCC3/XPB Both XPD and XPB proteins belong to the 10-subunit complex transcription factor IIH (TFIIH) that plays a key role in transcription and nucleotide excision repair, the DNA repair pathway devoted to the removal of ultraviolet-induced DNA lesions. Compelling evidence suggests that mutations affecting the DNA repair activity of TFIIH are responsible for the pathological features of XP, whereas those also impairing transcription give rise to TTD. By adopting a relatives-based whole transcriptome sequencing approach followed by specific gene expression profiling in primary fibroblasts from a large cohort of TTD or XP cases with mutations in ERCC2/XPD gene, we identify the expression alterations specific for TTD primary dermal fibroblasts. While most of these transcription deregulations do not impact on the protein level, very low amounts of prostaglandin I₂ synthase (PTGIS) are found in TTD cells. PTGIS catalyzes the last step of prostaglandin I₂ synthesis, a potent vasodilator and inhibitor of platelet aggregation. Its reduction characterizes all TTD cases so far investigated, both the PS-TTD with mutations in TFIIH coding genes as well as the nonphotosensitive (NPS)-TTD. A severe impairment of TFIIH and RNA polymerase II recruitment on the PTGIS promoter is found in TTD but not in XP cells. Thus, PTGIS represents a biomarker that combines all PS- and NPS-TTD cases and distinguishes them from XP.

Novel ERCC2 mutation in two siblings with trichothiodystrophy

Trichothiodystrophy describes a group of recessively inherited multisystem neuroectodermal disorders that takes its name from the characteristic feature of brittle, sulfur-deficient hair. We describe two siblings with trichothiodystrophy due to a novel genotype. The maternal mutation (p.Arg722Trp) is a previously described pathogenic mutation in ERCC2 that has been shown to result in a severe phenotype, while the paternal mutation (c.1480-1G > C) has not been previously reported. Our cases confirm the severe phenotype associated with the p.Arg722Trp mutation and expand the known genetic mutations associated with trichothiodystrophy by demonstrating a novel pathogenic mutation in ERCC2.