Mutation analysis of HPS1, the gene mutated in Hermansky-Pudlak syndrome, in patients with isolated platelet dense-granule deficiency

Background and objectives: isolated platelet dense granule (PDG) deficiency is a heterogeneous disorder frequently found among patients with mild to moderate bleeding diatheses. However, the molecular basis of this disorder is unknown. Genes involved in other rare bleeding disorders with associated reduction in the numbers of platelet dense-granules may play a role in isolated PDG deficiency. Among such genes, HPS1 is known to play a key role in the genesis of PDG and as many as 18 different HPS1 mutations have been identified in patients with Hermansky-Pudlak syndrome. Recently, we have identified subjects with one HPS1 heterozygous mutation displaying significant reductions in PDG without the clinical phenotype of Hermansky-Pudlak syndrome. This suggested that HPS1 mutations could be involved in isolated PDG deficiency. Design and methods: we sequenced all coding exons, and flanking intron regions of HPS1 in 16 patients with mild to severe PDG deficiency, most of whom had mild bleeding episodes. Nine patients reported a familial history of bleeding diathesis with PDG deficiency. We also evaluated the prevalence of HPS1 variations in 215 controls. Transmission electron microscopy was used to evaluate the number and morphology of PDG from patients and selected controls. Results: no patient with PDG deficiency carried severe mutations of the HPS1 gene. We identified 6 previously described and 5 new polymorphisms in the HPS1 gene. Platelet electron microscopy in controls carrying these polymorphisms revealed that they did not significantly modify the number or morphology of PDG. Interpretation and conclusions: mutations affecting the HPS1 gene play a minor role in isolated PDG deficiency. These results support a molecular heterogeneity responsible for the number and morphology of PDG

Involvement of stanniocalcins in the deregulation of glycaemia in obese mice and type 2 diabetic patients

Las estanniocalcinas se expresan en el tejido del páncreas, y se sugirió una correlación directa entre la insulina circulante y las concentraciones de STC2 en el ser humano. Aquí, mostramos una correlación significativa entre STC1 y tanto la glucemia como la hemoglobina glicosilada entre los pacientes con DM2, mientras que los pacientes con DM2 que presentan los mayores valores de hemoglobina glicosilada exhibieron la menor expresión de STC2. Sin embargo, el tratamiento de los pacientes con fármacos antiglicémicos no modifica significativamente la expresión de ambas STC. Por otra parte, los ratones STC2-/- que mostraron sobrepeso neonatal y adulto presentaron además una glucemia desregulada cuando fueron alimentados con una dieta hipercalórica (pellet de cría, BP). Esta alteración es más evidente en las primeras etapas de la vida animal. La glucemia desregulada en estos ratones se confirmó mediante una prueba oral de glucosa. Además, los ratones STC2-/- presentan un aumento del tamaño del páncreas; así, el análisis histológico revela que los ratones WT responden a la dieta BP aumentando el tamaño de los islotes pancreáticos a través de la inducción de la división celular, y los ratones STC2-/- carecen de este mecanismo compensatorio. Contrariamente, los ratones alimentados con STC2-/- muestran un mayor número de islotes pero de tamaño similar a los alimentados con el pellet regular. El análisis histopatológico demuestra la alteración de la estructura de los tejidos y las infiltraciones de eritrocitos en los ratones STC2-/-, posiblemente debido al estrés evocado por la dieta BP. Por último, se observó una mayor inmunotinción de glucagón en el islote de los ratones STC2-/-, y el ensayo ELISA de glucagón confirmó el aumento del glucagón circulante. En resumen, presentamos pruebas del papel de los STC, principalmente el STC2, como posible marcador temprano durante el desarrollo de la diabetes mellitus.Stanniocalcins are expressed in the pancreas tissue, and it was suggested a direct correlation between circulating insulin and STC2 concentrations in human. Here, we show a significant correlation between STC1 and both glycaemia and glycosylated haemoglobin among DM2 patients, while DM2 patients who present the greatest glycosylated haemoglobin values exhibited the lowest STC2 expression. However, treatment of patients with antiglycaemic drugs does not significantly modify the expression of both STCs. On the other hand, STC2-/- mice that exhibited neonatal and adult overweight further presented deregulated glycaemia when they were feed with a hypercaloric diet (breeding pellet, BP). This alteration is more evident at the early stages of the animal life. Deregulated glycaemia in these mice was confirmed using glucose oral test. In addition, STC2-/- mice present enhanced pancreas size; thus, the histological analysis reveals that WT mice respond to BP diet by increasing the size of the pancreatic islets through inducing cell division, and STC2-/- mice lack this compensatory mechanism. Contrary, BP fed STC2-/- mice show enhanced number of islets but of similar size than those fed with regular pellet. Histopathological analysis demonstrates tissue structure disruption and erythrocytes infiltrations in STC2-/- mice, possibly due to the stress evoked by the BP diet. Finally, enhanced glucagon immunostaining was observed in the islet of STC2-/- mice, and the glucagon ELISA assay confirmed the increase in the circulating glucagon. Summarizing, we present evidence of the role of STCs, mainly STC2, as a possible early marker during development of diabetes mellitus.• Ministerio de Economía y Competitividad. Becas 2013‐45564C2‐1‐P, BFU‐2016‐74932‐C2‐1‐P • Programa Juan de la Cierva. Becas IJCI‐2015‐25665, JC‐2012‐ 2934 • Junta de Extremadura. Beca PRIIB16046peerReviewe

A nonsense polymorphism in the protein Z-dependent protease inhibitor increases the risk for venous thrombosis

The protein Z-dependent protease inhibitor (ZPI) is a hemostatic serpin with anticoagulant activity. As for antithrombin, deficiency of ZPI could have relevant thrombotic consequences. We have studied 6 genetic modifications affecting the ZPI gene, identifying 5 haplotypes. Haplotype H5 is featured by a stop codon at position 67. The relevance of these genetic modifications and haplotypes in venous thrombosis was evaluated in a case-control study including 1018 patients and 1018 age- and sex-matched controls. Surprisingly, the H5 haplotype was found in 0.9% of controls, supporting that the Arg67Stop change is a low frequency nonsense polymorphism. The prevalence of this haplotype increased significantly in patients (3.0%), one of whom was in a homozygous state. Multivariate analysis confirms that carriers have a 3.3-fold risk of developing venous thrombosis (P = .002; 95% CI: 1.5-7.1). Moreover, we observed a significant association of this polymorphism with familial history of thrombosis (P < .001). Our study supports that the ZPI Arg67Stop nonsense polymorphism might be an independent genetic risk factor for venous thrombosis. This polymorphism has slightly lower prevalence but similar thrombotic risk than the FV Leiden or prothrombin 20210A. Although further studies are required, all available data support that the ZPI is a candidate to play a significant role in thrombosis and should be evaluated in thrombophilic studies. (Blood. 2006;108:177-183