Novel Homozygous Mutations in the Genes TGM1, SULT2B1, SPINK5 and FLG in Four Families Underlying Congenital Ichthyosis

Human sulfotransferase SULT2B1 physiological role and the impact of genetic polymorphism on enzyme activity and pathological conditions

Human SULT2B1gene is responsible for expressing SULT2B1a and SULT2B1b enzymes, which are phase II metabolizing enzymes known as pregnenolone and cholesterol sulfotransferase (SULT), respectively. They are expressed in several tissues and contribute to steroids and hydroxysteroids homeostasis. Genetic variation of the SULT2B1 is reported to be associated with various pathological conditions, including autosomal recessive ichthyosis, cardiovascular disease, and different types of cancers. Understanding the pathological impact of SULT2B1 genetic polymorphisms in the human body is crucial to incorporating these findings in evaluating clinical conditions or improving therapeutic efficacy. Therefore, this paper summarized the most relevant reported studies concerning SULT2B1 expression, tissue distribution, substrates, and reported genetic polymorphisms and their mechanisms in enzyme activity and pathological conditions.

Biallelic mutations in FLG, TGM1, and STS genes segregated with different types of ichthyoses in eight families of Pakistani origin

BACKGROUND

Congenital ichthyosis is a diverse group of keratinization disorders associated with generalized scaling of skin of varying severity. The non-syndromic forms of congenital ichthyosis are further grouped into common ichthyosis (ichthyosis vulgaris and X-linked ichthyosis), autosomal recessive congenital ichthyosis, and keratopathic ichthyosis.

OBJECTIVE

To identify sequence variants involved in different forms of hereditary ichthyoses.

METHODS

We studied eight families with different types of ichthyosis including four families with autosomal recessive congenital ichthyosis and four families with common ichthyosis. Whole exome sequencing and PCR based genotyping was carried out to find out the molecular basis of disease.

RESULTS

In one family, a novel duplication sequence variant NM_002016.2:c.2767dupT; NP_002007.1:p.Ser923PhefsTer2 was identified in FLG gene; in four families a previously reported nonsense sequence variant NM_000359.3:c.232C>T; NP_002007.1:p.Arg78Ter was identified in TGM1 gene, while, in three families of X-linked recessive ichthyosis, the whole STS gene (NM_001320752.2; NP_001307681.2) regions were deleted.

STUDY LIMITATION

Gene expression studies have not been performed that would have strengthened the findings of computational analysis.

CONCLUSION

This study highlights the significance of the c.232C>T variant in the TGM1 gene as a possible founder mutation, complete STS gene deletion as reported previously in Pakistani population, while novel sequence variant in the FLG gene expands the spectrum of variations in this gene. These findings may be used for genetic counseling of the studied families.

Ichthyosis vulgaris: An updated review

Ichthyosis vulgaris is an inherited, non-syndromic form of ichthyosis that presents with skin problems. Making up more than 95% cases of ichthyosis, ichthyosis vulgaris is caused by heterozygous loss-of-function mutation of the filaggrin gene, raising the fragility and permeability of the stratum corneum. It typically presents in infancy as xerosis, skin lesions, keratosis pilaris, palmoplantar hyper linearity, scaly dermatosis, and erythroderma, clearly identifiable by age 5. Although majority of patients have a normal lifespan, possible complications include a vitamin D deficiency and auditory problems due to scaling in the ears, besides a drop in quality of life due to dermatological changes. Urea-based creams with 10% urea, ceramides, and other ceramides are often the first line therapy in ichthyosis vulgaris. There is no known curative treatment for ichthyosis vulgaris, but lifelong treatment can alleviate the symptoms. Urea-based creams are highly therapeutic, whereas ammonium lactate 12% lotion with a physiological lipid-based repair cream can help with scaling and dryness. There is also evidence in favour of propylene glycol solutions. Risankizumab, an anti-interleukin-23 drug, and enhancement of natural moisturizing factors are also two highly promising solutions that require additional research. This review aims to provide updates on the manifestation, evaluation, and treatment of ichthyosis vulgaris.

Congenital Ichthyosis: Clinical and Genetic Characteristics of the Disease

Congenital ichthyosis is a group (almost 100 clinical variants) of rare genetic skin diseases caused by pathogenic changes in more than 50 genes. Clinical features of ichthyosis, regardless of its genotype, are dry skin, peeling, hyperkeratosis frequently accompanied with erythroderma. These patients have extremely low quality of life due to changes in appearance, discomfort due to itching and functional limitations (pain during walking, impaired hands motor skills and functions due to hyperkeratosis foci in functionally relevant areas), as well as impaired functions of various organs and systems in syndromic forms of disease. Patients need daily skin care and systemic medications. By now, there is no definitive treatment for ichthyosis. Diagnostic difficulties in determining the clinical forms of congenital ichthyosis are associated with their clinical heterogeneity and with similarity in external manifestations. Difficulties in differential diagnosis with other dermatoses are particularly crucial in case of syndromic forms of disease. This review presents the modern classification of ichthyoses, provides data on disease clinical and genetic variants, diagnostic algorithms, treatment methods for patients with this severe disease.

Copy number variation characterization and possible candidate genes in miscarriage and stillbirth by next-generation sequencing analysis

Background

The present study aimed to explore the etiological relationship between miscarriage and stillbirth and copy number variations (CNVs), as well as provide useful genetic guidance for high‐risk pregnancy.

Methods

In total, 659 fetal samples were recruited and subjected to DNA extraction and CNV sequencing (CNV‐seq), relevant medical records were collected.

Results

There were 322 cases (48.86%) with chromosomal abnormalities, including 230 with numerical abnormalities and 92 with structural abnormalities. Chromosomal monosomy variations mainly occurred on sex chromosomes and trisomy variations mainly occurred on chromosomes 16, 22, 21, 18, 13 and 15. In total, 41 pathogenic CNVs (23 microdeletions and 18 microduplications) were detected in 27 fetal tissues. The rates of numerical chromosomal abnormalities were 29.30% (109/372), 32.39% (57/176) and 57.66% (64/111) in < 30‐year‐old, 30–34‐year‐old and ≥ 35‐year‐old age pregnant women, respectively, and increased with an increasing age (p < 0.001). There was statistically significant difference (χ² = 7.595, p = 0.022) in the rates of structural chromosomal abnormalities in these groups (13.71%, 18.75% and 7.21%, respectively). The rates of numerical chromosomal abnormalities were 45.44% (219/482), 7.80% (11/141) and 0% (0/36) in the ≤ 13 gestational weeks, 14–27 weeks and ≥ 28 weeks groups, respectively, and decreased with respect to the increasing gestational age of the fetuses (p < 0.001).

Conclusions

The present study has obtained useful and accurate genetic etiology information that will provide useful genetic guidance for high‐risk pregnancies.

Report of a Novel ALOX12B Mutation in Self-Improving Collodion Ichthyosis with an Overview of the Genetic Background of the Collodion Baby Phenotype

Collodion baby is a congenital, transient phenotype encountered in approximately 70–90% of autosomal recessive congenital ichthyosis and is an important entity of neonatal erythroderma. The clinical outcome after this severe condition is variable. Genetic mutations of components of the epidermal lipoxygenase pathway have been implicated in the majority of self-improving collodion ichthyosis (SICI). In SICI, the shedding of the collodion membrane reveals clear skin or only mild residual manifestation of ichthyosis. Here we report the case of a girl born with a severe form of collodion baby phenotype, whose skin almost completely cleared within the first month of life. At the age of 3 years, only mild symptoms of a keratinization disorder remained. However, the severity of erythema and scaling showed mild fluctuations over time. To objectively evaluate the skin changes of the patient, we assessed the ichthyosis severity index. Upon sequencing of the ALOX12B gene, we identified a previously unreported heterozygous nonsense mutation, c.1607G>A (p.Trp536Ter) with the recurrent, heterozygous mutation c.1562A>G (p.Tyr521Cys). Thereby, our findings expand the genotypic spectrum of SICI. In addition, we summarize the spectrum of further genetic diseases that can present at birth as collodion baby, in particular the SICI.