Platelet defects in congenital variant of Rett syndrome patients with FOXG1 mutations or reduced expression due to a position effect at 14q12.

The Forkhead box G1 (FOXG1) gene encodes a transcriptional repressor essential for early development of the telencephalon. Intragenic mutations and gene deletions leading to haploinsufficiency cause the congenital variant of Rett syndrome. We here describe Rett syndrome-like patients, three of them carrying a balanced translocation with breakpoint in the chromosome 14q12 region, and one patient having a 14q12 microdeletion excluding the FOXG1 gene. The hypothesis of long-range FOXG1-regulatory elements in this region was supported by our finding of reduced FOXG1 mRNA and protein levels in platelets and skin fibroblasts from these cases. Given that FOXG1 is not only expressed in brain but also in platelets, we have studied platelet morphology in these patients and two additional patients with FOXG1 mutations. Electron microscopy of their platelets showed some enlarged, rounder platelets with often abnormal alpha, and fewer dense granules. Platelet function studies were possible in one 14q12 translocation patient with a prolonged Ivy bleeding time and a patient with a heterozygous FOXG1 c.1248C>G mutation (p.Tyr416X). Both have a prolonged PFA-100 occlusion time with collagen and epinephrine and reduced aggregation responses to low dose of ADP and epinephrine. Dense granule ATP secretion was normal for strong agonists but absent for epinephrine. In conclusion, our study shows that by using platelets functional evidence of cis-regulatory elements in the 14q12 region result in reduced FOXG1 levels in patients' platelets having translocations or deletions in that region. These platelet functional abnormalities deserve further investigation regarding a non-transcriptional regulatory role for FOXG1 in these anucleated cells.

NPC1 defect results in abnormal platelet formation and function: studies in Niemann-Pick disease type C1 patients and zebrafish.

Niemann-Pick type C is a lysosomal storage disease associated with mutations in NPC1 or NPC2, resulting in an accumulation of cholesterol in the endosomal-lysosomal system. Niemann-Pick type C has a clinical spectrum that ranges from a neonatal rapidly fatal disorder to an adult-onset chronic neurodegenerative disease combined with remarkably, in some cases, hematological defects such as thrombocytopenia, anemia and petechial rash. A role of NPC1 in hematopoiesis was never shown. Here, we describe platelet function abnormalities in three unrelated patients with a proven genetic and biochemical NPC1 defect. Their platelets have reduced aggregations, P-selectin expression and ATP secretions that are compatible with the observed abnormal alpha and reduced dense granules as studied by electron microscopy and CD63 staining after platelet spreading. Their blood counts were normal. NPC1 expression was shown in platelets and megakaryocytes (MKs). In vitro differentiated MKs from NPC1 patients exhibit hyperproliferation of immature MKs with different CD63(+) granules and abnormal cellular accumulation of cholesterol as shown by filipin stainings. The role of NPC1 in megakaryopoiesis was further studied using zebrafish with GFP-labeled thrombocytes or DsRed-labeled erythrocytes. NPC1 depletion in zebrafish resulted in increased cell death in the brain and abnormal cellular accumulation of filipin. NPC1-depleted embryos presented with thrombocytopenia and mild anemia as studied by flow cytometry and real-time QPCR for specific blood cell markers. In conclusion, this is the first report, showing a role of NPC1 in platelet function and formation but further studies are needed to define how cholesterol storage interferes with these processes.

Mucosal gene expression of antimicrobial peptides in inflammatory bowel disease before and after first infliximab treatment.

BACKGROUND: Antimicrobial peptides (AMPs) protect the host intestinal mucosa against microorganisms. Abnormal expression of defensins was shown in inflammatory bowel disease (IBD), but it is not clear whether this is a primary defect. We investigated the impact of anti-inflammatory therapy with infliximab on the mucosal gene expression of AMPs in IBD. METHODOLOGY/PRINCIPAL FINDINGS: Mucosal gene expression of 81 AMPs was assessed in 61 IBD patients before and 4-6 weeks after their first infliximab infusion and in 12 control patients, using Affymetrix arrays. Quantitative real-time reverse-transcription PCR and immunohistochemistry were used to confirm microarray data. The dysregulation of many AMPs in colonic IBD in comparison with control colons was widely restored by infliximab therapy, and only DEFB1 expression remained significantly decreased after therapy in the colonic mucosa of IBD responders to infliximab. In ileal Crohn's disease (CD), expression of two neuropeptides with antimicrobial activity, PYY and CHGB, was significantly decreased before therapy compared to control ileums, and ileal PYY expression remained significantly decreased after therapy in CD responders. Expression of the downregulated AMPs before and after treatment (DEFB1 and PYY) correlated with villin 1 expression, a gut epithelial cell marker, indicating that the decrease is a consequence of epithelial damage. CONCLUSIONS/SIGNIFICANCE: Our study shows that the dysregulation of AMPs in IBD mucosa is the consequence of inflammation, but may be responsible for perpetuation of inflammation due to ineffective clearance of microorganisms.