Search

Lipid metabolism influences stem cell maintenance and differentiation but genetic factors that control these processes remain to be delineated. Here, we identify Tnfaip2 as an inhibitor of reprogramming of mouse fibroblasts into induced pluripotent stem cells. Tnfaip2 knockout impairs differentiation of embryonic stem cells (ESCs), and knockdown of the planarian para-ortholog, Smed-exoc3, abrogates in vivo tissue homeostasis and regeneration—processes that are driven by somatic stem cells. When stimulated to differentiate, Tnfaip2-deficient ESCs fail to induce synthesis of cellular triacylglycerol (TAG) and lipid droplets (LD) coinciding with reduced expression of vimentin (Vim)—a known inducer of LD formation. Smed-exoc3 depletion also causes a strong reduction of TAGs in planarians. The study shows that Tnfaip2 acts epistatically with and upstream of Vim in impairing cellular reprogramming. Supplementing palmitic acid (PA) and palmitoyl-L-carnitine (the mobilized form of PA) restores the differentiation capacity of Tnfaip2-deficient ESCs and organ maintenance in Smed-exoc3-depleted planarians. Together, these results identify a novel role of Tnfaip2 and exoc3 in controlling lipid metabolism, which is essential for ESC differentiation and planarian organ maintenance., publishedVersion

The principal cause of β-thalassemia (or β-thalassemia major) is the presence of free α chains that cause severe damage to red blood cells. Clinical manifestations of the disease are attenuated in cases known as β-thalassemia intermedia that do not require transfusions. While some cases of β- thalassemia intermedia correlate with the presence of 2 β+alleles, i.e. alleles that do not abolish synthesis of β chains, other patients affected with this mild condition bear 2 β0 alleles and for them the explanation for the mild phenotype is the synthesis of fetal γ-globin that persists in adult life and that associating with free α chains produces fetal hemoglobin (HbF). It has been proposed that this unusual production might be due to polymorphic sequences located on the β-globin cluster that might affect transcription factor binding. These polymorphic sites are represented by single nucleotide polymorphisms (SNPs) and microsatellites located in intragenic regions like (TG)m(CG)n in IVS2 of fetal genes, or in their proximal and distal promoters; the microsatellite (AT)XTY at -540 of the β globin gene; and the microsatellite (AT)XNY(AT)Z located in the hypersensitive site (HS2) of the β globin locus control region LCR. We investigated these polymorphic sites and their linkage to the β-thalassemic mutations typical of the β0-Sardinian thalassemic patients. In fact, 10% of them manifest intermediate thalassemia due to persistent production of HbF in adults. We analyzed four categories of patients: 1) β-thalassemic patients affected with transfusion-dependent Thalassemia Major (genotypes β039/β039 and β039/β +-87); 2) patients homozygous for transfusion-independent Thalassemia Intermedia (β039/β039); 3) heterozygotes for different β-thalassemic mutations (β039, β+IVS1-nt6) that present high levels of HbF; and 4) normal subjects. We identified a new (never described in literature) polymorphic microsatellite in the IVS2 of the Gγ and Aγ genes, and in the distal promoter of β gene. None of the patients examined presented the ndHPFH mutations and in all we ruled out the presence of the α-thalassemia mutations more widespread in Sardinia and the Mediterranean. We confirmed that the Thalassemia Intermedia (mild) patients were homozygous for the mutation β039 (CAG→ TAG), the same presented in 90% of patients affected by Thalassemia Major. The β039 mutation resulted distributed on different polymorphic configurations, none of which identical to those described in literature: two of them in association with the II haplotype of Orkin and the AγT allele, and two with haplotype I and the AγI allele. The β+-87 mutation located on chromosome with the polymorphic configuration 7a, resulted linked to the haplotype VIII of Orkin, while the locus β+IVS1-nt6 (8a) to the haplotipe II. Presence of the same polymorphic configuration (1a) on 75% of the chromosomes of the intermediate patients and 67,5% of the transfused patients rules out the hypothesis that this configuration can carry out a role of modulation of the expression of HbF in Sardinian patients.