Loss of GATA-1 full length as a cause of Diamond-Blackfan anemia phenotype

Mutations in the hematopoietic transcription factor GATA-1 alter the proliferation/differentiation of hemopoietic progenitors. Mutations in exon 2 interfere with the synthesis of the full-length isoform of GATA-1 and lead to the production of a shortened isoform, GATA-1s. These mutations have been found in patients with Diamond-Blackfan anemia (DBA), a congenital erythroid aplasia typically caused by mutations in genes encoding ribosomal proteins. We sequenced GATA-1 in 23 patients that were negative for mutations in the most frequently mutated DBA genes. One patient showed a c.2T > C mutation in the initiation codon leading to the loss of the full-length GATA-1 isoform

Melanoma-prone families: new evidence of distinctive clinical and histological features of melanomas in CDKN2A mutation carriers.

Germline mutations on the CDKN2A gene, the most important known genetic factors associated with cutaneous melanomas (CMs), predispose carriers to multiple primary CMs (MPMs) with higher frequency and younger onset compared to non-carriers. Most of the largest published studies concerning clinical and histological characteristics of CMs with CDKN2A mutation carriers did not specify if the described CMs are first or subsequent to the first, and they used sporadic CMs from non-genotyped patients as controls. We conducted a single-centre observational study to compare clinical and histological CM features of 32 unrelated carriers (MUT) of 5 germline CDKN2A mutations (one of which was never previously described) compared to 100 genotyped wild-type (WT) patients. We stratified the data based on time of diagnosis, anatomical site and histological subtype of CMs, demonstrating several significant unreported differences between the two groups. MUT developed a higher number of dysplastic nevi and MPMs. We proved for the first time that anatomical distribution of CMs in MUT was independent of gender, unlike WTs. MUTs developed in situ and superficial spreading melanomas (SSMs) more frequently, with significantly higher number of SSMs on the head/neck. In MUTs, Breslow thickness was significantly lower for all invasive CMs. When CMs were stratified on the basis of the time of occurrence, statistical significance was maintained only for SSMs subsequent to the first. In WTs, Clark level was significantly higher, and ulceration was more prevalent than in MUTs. Significant differences in ulceration were observed only in SSMs. In nodular CMs, we did not find differences in terms of Breslow thickness or ulceration between WTs and MUTs. In situ CMs developed 10 years earlier in MUTs with respect to WTs, whereas no significant differences were observed in invasive CMs. In contrast to those reported previously by other authors, we did not find a difference in skin phototype

A functional assay for the clinical annotation of genetic variants of uncertain significance in Diamond\u2013Blackfan anemia

Diamond-Blackfan anemia (DBA) is a rare genetic hypoplasia of erythroid progenitors characterized by mild to severe anemia and associated with congenital malformations. Clinical manifestations in DBA patients are quite variable and genetic testing has become a critical factor in establishing a diagnosis of DBA. The majority of DBA cases are due to heterozygous loss-of-function mutations in ribosomal protein (RP) genes. Causative mutations are fairly straightforward to identify in the case of large deletions and frameshift and nonsense mutations found early in a protein coding sequence, but diagnosis becomes more challenging in the case of missense mutations and small in-frame indels. Our group recently characterized the phenotype of lymphoblastoid cell lines established from DBA patients with pathogenic lesions in RPS19 and observed that defective pre-rRNA processing, a hallmark of the disease, was rescued by lentiviral vectors expressing wild-type RPS19. Here, we use this complementation assay to determine whether RPS19 variants of unknown significance are capable of rescuing pre-rRNA processing defects in these lymphoblastoid cells as a means of assessing the effects of these sequence changes on the function of the RPS19 protein. This approach will be useful in differentiating pathogenic mutations from benign polymorphisms in identifying causative genes in DBA patients

Lymphoblastoid cell lines from Diamond Blackfan anaemia patients exhibit a full ribosomal stress phenotype that is rescued by gene therapy

Diamond Blackfan anaemia (DBA) is a congenital bone marrow failure syndrome characterised by selective red cell hypoplasia. DBA is most often due to heterozygous mutations in ribosomal protein (RP) genes that lead to defects in ribosome biogenesis and function and result in ribosomal stress and p53 activation. The molecular mechanisms underlying this pathology are still poorly understood and studies on patient erythroid cells are hampered by their paucity. Here we report that RP-mutated lymphoblastoid cell lines (LCLs) established from DBA patients show defective rRNA processing and ribosomal stress features such as reduced proliferation, decreased protein synthesis, and activation of p53 and its target p21. These phenotypic alterations were corrected by gene complementation. Our data indicate that DBA LCLs could be a useful model for molecular and pharmacological investigations