Detection of a rare CDKN2A intronic mutation in a Hungarian melanoma-prone family and its role in splicing regulation

Case report: A case of epidermolysis bullosa complicated with pyloric atresia and a literature review

Objective

This article aims to explore the diagnosis, molecular characteristics, treatment, and prognosis of epidermolysis bullosa with pyloric atresia (EB-PA).

Methods

The clinical manifestations, diagnosis and treatment, and genetic characteristics of a patient with EB-PA admitted to our hospital were analysed. The disease subtypes, concomitant abnormalities, molecular characteristics, and prognosis of patients with EB-PA were summarized by searching the EB-PA-related literature since 2011.

Results

We present a very low birth weight female infant with skin blisters and pyloric obstruction. Exome sequencing revealed heterozygous mutations in the ITGB4 gene: c.794dupC (p. S265fs*5) and c.2962G > A (p.A988T). This infant was diagnosed with EB-PA. Coverage of the wounds and Penicillin were used to prevent infection, but the patient eventually developed severe sepsis. A literature review was carried out including 49 cases of EB-PA; among these cases, 34 were preterm infants, weighing between 930 and 3,640 g. Of these EB-PA patients, 28 had accompanying malformations, including urinary system malformations and aplasia cutis congenita (ACC). Thirty-two patients identified the subtype of EB-PA, of whom 25 were diagnosed with junctional epidermolysis bullosa (JEB), 6 with epidermolysis bullosa simplex (EBS), and 1 with dystrophic epidermolysis bullosa (DEB). Genetic testing was conducted on 23 patients, of whom 15 carried Integrin Beta-4 (ITGB4) gene mutations and one JEB patient carried an Integrin Alpha-6 (ITGA6) gene mutation; 4 of the 5 EBS patients had Plectin (PLEC) gene mutations, and the other had an ITGB4 mutation. ITGB4 mutation cases involved 29 mutation sites, primarily concentrated in the region encoding the integrin beta subunit; PLEC mutation cases involved 7 mutation sites. Among all cases, 43 underwent pyloric atresia surgery, of whom 24 died postoperatively, and 6 without surgery therapy died within a short period.

Conclusion

EB-PA is a rare genetic disorder characterized by increased skin fragility and PA involving mutations in the ITGB4, PLEC, or ITGA6 genes. EB-PA has a high incidence of complications and mortality, surgery and supportive therapy are currently the most common treatment options.

Intronic variants of MITF (rs7623610) and CREB1 (rs10932201) genes may enhance splicing efficiency in human melanoma cell line

We previously reported that intronic single nucleotide variations (SNVs) in MITF (c.938-325G>A, rs7623610) and CREB1 (c.303+373G>A, rs10932201) genes were associated with risk, aggressiveness, and prognosis of cutaneous melanoma (CM). In this study, we investigated the influence of the above SNVs in splicing patterns and efficiency. We constructed minigenes with wild type and variant alleles from MITF and CREB1 to assess the effect of the SNVs on splicing. The minigenes were transfected in the human melanoma cell line (SK-MEL-28). RT-PCR and DNA sequencing investigated the constructs' splicing patterns. Minigenes constructs' splicing efficiency and HNRNPA1 and SF1 splicing genes' expression were investigated by qPCR. We found that MITF and CREB1 SNVs did not alter the splicing pattern, but they influenced the splicing efficiency. MITF-A (p= 0.03) and CREB1-A (p= 0.005) variant minigenes yielded an increase of mRNA generated from the constructions. Additionally, lower mRNA levels of HNRNPA1 and SF1 were seen in the variant minigenes MITF-A (p= 0.04) and CREB1-A (p= 0.005). We described for the first time the potential importance of MITF rs7623610 and CREB1 rs10932201 SNVs in splicing efficiency and its relationship with CM.

Absence of germline CDKN2A mutation in Sicilian patients with familial malignant melanoma: Could it be a population-specific genetic signature?

Germline CDKN2A mutations have been described in 25% to 40% of melanoma families from several countries. Sicilian population is genetically different from the people of Europe and Northern Italy because of its historical background, therefore familial melanoma could be due to genes different from high-penetrance CDKN2A gene. Four hundred patients with cutaneous melanoma were observed in a 6-years period at the Plastic Surgery Unit of the University of Palermo. Forty-eight patients have met the criteria of the Italian Society of Human Genetics (SIGU) for the diagnosis of familial melanoma and were screened for CDKN2A and CDK4 mutations. Mutation testing revealed that none of the families carried mutations in CDK4 and only one patient harboured the rare CDKN2A p.R87W mutation. Unlike other studies, we have not found high mutation rate of CDKN2A in patients affected by familial melanoma or multiple melanoma. This difference could be attributed to different factors, including the genetic heterogeneity of the Sicilian population. It is likely that, as in the Australian people, the inheritance of familial melanoma in this island of the Mediterranean Sea is due to intermediate/low-penetrance susceptibility genes, which, together with environmental factors (as latitude and sun exposure), could determine the occurrence of melanoma.

Novel CDKN2A mutations in Austrian melanoma patients

CDKN2A is the most prominent familial melanoma gene, with mutations occurring in up to 40% of the families. Numerous mutations in the gene are known, several of them representing regional founder mutations. We sought to determine, for the first time, germline mutations in CDKN2A in Austria to identify novel mutations. In total, 700 individuals (136 patients with a positive family history and 164 with at least two primary melanomas as the high-risk groups; 200 with single primary melanomas; and 200 healthy individuals as the control groups) were Sanger sequenced for CDKN2A exon 1α, 1β, and 2. The 136 patients with affected relatives were also sequenced for CDK4 exon 2. We found the disease-associated mutations p.R24P (8×), p.N71T (1×), p.G101W (1×), and p.V126D (1×) in the group with affected relatives and p.R24P (2×) in the group with several primary melanomas. Furthermore, we discovered four mutations of unknown significance, two of which were novel: p.A34V and c.151-4 G>C, respectively. Computational effect prediction suggested p.A34V as conferring a high risk for melanoma, whereas c.151-4 G>C, although being predicted as a splice site mutation by MutationTaster, could not functionally be confirmed to alter splicing. Moreover, computational effect prediction confirmed accumulation of high-penetrance mutations in high-risk groups, whereas mutations of unknown significance were distributed across all groups. p.R24P is the most common high-risk mutation in Austria. In addition, we discovered two new mutations in Austrian melanoma patients, p.A34V and c.151-4 G>C, respectively.