Unravelling the disease mechanism for TSPYL1 deficiency.

We describe a lethal combined nervous and reproductive systems disease in three affected siblings of a consanguineous family. The phenotype was characterized by visceroautonomic dysfunction (neonatal bradycardia/apnea, feeding problems, hyperactive startle reflex), severe postnatal progressive neurological abnormalities (including abnormal neonatal cry, hypotonia, epilepsy, polyneuropathy, cerebral gray matter atrophy), visual impairment, testicular dysgenesis in males and sudden death at infant age by brainstem-mediated cardiorespiratory arrest. Whole-exome sequencing revealed a novel homozygous frameshift variant p.

The transcription factor GATA1 regulates NBEAL2 expression through a long-distance enhancer.

Gray platelet syndrome is named after the gray appearance of platelets due to the absence of α-granules. It is caused by recessive mutations in , resulting in macrothrombocytopenia and myelofibrosis. Though using the term gray platelets for GATA1 deficiency has been debated, a reduced number of α-granules has been described for macrothrombocytopenia due to mutations.

Methylome analysis for spina bifida shows hypomethylation as a risk factor with evidence for a complex (epi)genetic interplay to affect neural tube development.

Background: Neural tube defects (NTDs) are severe congenital malformations that arise from failure of neurulation during early embryonic development. The molecular basis underlying most human NTDs still remains largely unknown. Based on the hypothesis that folic acid prevents NTDs by stimulating methylation reactions, DNA methylation changes could play a role in NTDs.

A dominant gain-of-function mutation in universal tyrosine kinase SRC causes thrombocytopenia, myelofibrosis, bleeding, and bone pathologies.

The Src family kinase (SFK) member SRC is a major target in drug development because it is activated in many human cancers, yet deleterious SRC germline mutations have not been reported. We used genome sequencing and Human Phenotype Ontology patient coding to identify a gain-of-function mutation in SRC causing thrombocytopenia, myelofibrosis, bleeding, and bone pathologies in nine cases. Modeling of the E527K substitution predicts loss of SRC's self-inhibitory capacity, which we confirmed with in vitro studies showing increased SRC kinase activity and enhanced Tyr(419) phosphorylation in COS-7 cells overexpressing E527K SRC.

Platelet studies in autism spectrum disorder patients and first-degree relatives.

Background: Platelets have been proven to be a useful cellular model to study some neuropathologies, due to the overlapping biological features between neurons and platelets as granule secreting cells. Altered platelet dense granule morphology was previously reported in three autism spectrum disorder (ASD) patients with chromosomal translocations that disrupted ASD candidate genes NBEA, SCAMP5, and AMYSIN, but a systematic analysis of platelet function in ASD is lacking in contrast to numerous reports of elevated serotonin levels in platelets and blood as potential biomarker for ASD.

Methods: We explored platelet count, size, epinephrine-induced activation, and dense granule ATP secretion in a cohort of 159 ASD patients, their 289 first-degree relatives (103 unaffected siblings, 99 mothers, and 87 fathers), 45 adult controls, and 65 pediatric controls.

DNA methylation analysis of Homeobox genes implicates HOXB7 hypomethylation as risk factor for neural tube defects.

Neural tube defects (NTDs) are common birth defects of complex etiology. Though family- and population-based studies have confirmed a genetic component, the responsible genes for NTDs are still largely unknown. Based on the hypothesis that folic acid prevents NTDs by stimulating methylation reactions, epigenetic factors, such as DNA methylation, are predicted to be involved in NTDs.

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.

Methylation defect in imprinted genes detected in patients with an Albright's hereditary osteodystrophy like phenotype and platelet Gs hypofunction.

Background: Pseudohypoparathyroidism (PHP) indicates a group of heterogeneous disorders whose common feature is represented by impaired signaling of hormones that activate Gsalpha, encoded by the imprinted GNAS gene. PHP-Ib patients have isolated Parathormone (PTH) resistance and GNAS epigenetic defects while PHP-Ia cases present with hormone resistance and characteristic features jointly termed as Albright's Hereditary Osteodystrophy (AHO) due to maternally inherited GNAS mutations or similar epigenetic defects as found for PHP-Ib. Pseudopseudohypoparathyroidism (PPHP) patients with an AHO phenotype and no hormone resistance and progressive osseous heteroplasia (POH) cases have inactivating paternally inherited GNAS mutations.

Regulator of G-protein signaling 18 controls megakaryopoiesis and the cilia-mediated vertebrate mechanosensory system.

RGS18 was originally identified as a R4 subfamily member of regulators of G-protein signaling (RGS) with specific expression in hematopoietic progenitors, myeloerythroid cells, and megakaryocytes, though its physiological role in hematopoiesis remained unknown. Here, we show that lentiviral RGS18 overexpression during differentiation of mouse Sca1(+) hematopoietic stem cells induced a 50% increase of megakaryocyte proliferation. RGS18 depletion in zebrafish results in thrombocytopenia, as 66 to 88% of the embryos lack thrombocytes after injection of an ATG or splice-blocking morpholino, respectively.

No evidence for GNAS copy number variants in patients with features of Albright's hereditary osteodystrophy and abnormal platelet Gs activity.

Albright's hereditary osteodystrophy (AHO) is characterized by short stature, round face, calcifications, obesity, brachydactyly and intellectual disability. AHO without hormone resistance is called pseudopseudohypoparathyroidism (PPHP), a rare clinical condition difficult to diagnose with highly variable features. PPHP is caused by paternally inherited loss-of-function mutations in the GNAS.

Public vaccination programmes against hepatitis B in The Netherlands: assessing whether a targeted or a universal approach is appropriate.

To date, the policy to control hepatitis B in the Netherlands is to vaccinate specific risk groups, rather than all children. Low incidence of the disease has fueled debate whether such a targeted vaccination strategy or rather a universal strategy, as recommended by the World Health Organization, is appropriate. The standard framework for assessing whether a particular vaccination should be included in a public programme, as recently proposed by the Health Council of the Netherlands (HCN), was applied to the various options for hepatitis B vaccination.

Platelet Gs hypofunction and abnormal morphology resulting from a heterozygous RGS2 mutation.

Summary Background: Regulator of G-protein signaling (RGS) 2 negatively regulates Gs signaling by inhibiting the activation of adenylyl cyclase (AC). RGS2 mRNA contains four translation initiation sites, leading to four isoforms with different abilities to inhibit AC activity; the largest isoform is the most pronounced inhibitor. A role for RGS2 in platelets is not known.

Severe gastrointestinal bleeding and thrombocytopenia in a child with an anti-GATA1 autoantibody.

We describe a patient, who developed during the first week of life petechiae and hematomas caused by severe thrombocytopenia and gastrointestinal bleeding due to multiple small gastric hemangiomata. Bone marrow examination showed hypermegakaryocytosis and dysmegakaryopoiesis. Alloimmune thrombocytopenia was excluded.

A compound heterozygous mutation in glycoprotein VI in a patient with a bleeding disorder.

Background: The physiological relevance of the collagen glycoprotein VI (GPVI) receptor was known prior to its recognition as a platelet membrane receptor as several patients lacking GPVI as a consequence of autoantibody inhibition presented with a mild bleeding diathesis. Remarkably, patients with a proven GPVI gene mutation have not yet been identified.

Results: In the present study, we describe a patient with a lifelong history of bleeding problems, structurally normal platelets but a functional platelet defect.

GNAS defects identified by stimulatory G protein alpha-subunit signalling studies in platelets.

Context: GNAS is an imprinted region that gives rise to several transcripts, antisense transcripts, and noncoding RNAs, including transcription of RNA encoding the alpha-subunit of the stimulatory G protein (Gsalpha). The complexity of the GNAS cluster results in ubiquitous genomic imprints, tissue-specific Gsalpha expression, and multiple genotype-phenotype relationships. Phenotypes resulting from genetic and epigenetic abnormalities of the GNAS region include Albright's hereditary osteodystrophy, pseudohypoparathyroidism types Ia (PHPIa) and Ib (PHPIb), and pseudopseudohypoparathyroidism (PPHP).

Compound heterozygous mutations in the GNAS gene of a boy with morbid obesity, thyroid-stimulating hormone resistance, pseudohypoparathyroidism, and a prothrombotic state.

Context: Pseudohypoparathyroidism type Ia and pseudopseudohypoparathyroidism are characterized by Albright's hereditary osteodystrophy (AHO), respectively, with and without hormone resistance. Both clinical conditions result from decreased expression or function of the alpha-subunit of the stimulatory G protein (Gsalpha) of adenylyl cyclase due to heterozygous inactivating mutations in GNAS. Homozygous GNAS defects have not been described.

PACAP and its receptor VPAC1 regulate megakaryocyte maturation: therapeutic implications.

Megakaryocytes and platelets express the Gs-coupled VPAC1 receptor, for which the pituitary adenylyl cyclase-activating peptide (PACAP) and the vasointestinal peptide (VIP) are agonists. We here demonstrate a regulatory role for VPAC1 signaling during megakaryopoiesis. A total of 2 patients with trisomy 18p with PACAP overexpression and transgenic mice overexpressing PACAP in megakaryocytes have thrombopathy, a mild thrombocytopenia, and a reduced number of mature megakaryocytes in their bone marrow.

Increased Gs signalling in platelets and impaired collagen activation, due to a defect in the dystrophin gene, result in increased blood loss during spinal surgery.

Controversy exists regarding the cause of the significantly increased blood loss during spinal surgery in Duchenne muscular dystrophy (DMD) patients compared with similar surgery in other patients. DMD is caused by a mutation in the cytoskeletal dystrophin, which binds to extracellular matrix laminin and which has been described as a G-protein-coupled receptor. We hypothesized that disturbed cytoskeleton organization in DMD patients would alter Gs protein and collagen signalling in platelets, leading to dysfunctional platelets and a haemorrhagic tendency during surgery.

The microtubule-associated protein doublecortin-like regulates the transport of the glucocorticoid receptor in neuronal progenitor cells.

In neuronal cells, activated glucocorticoid receptor (GR) translocates to the nucleus guided by the cytoskeleton. However, the detailed mechanisms underlying GR translocation remain unclear. Using gain and loss of function studies, we report here for the first time that the microtubule-associated protein doublecortin-like (DCL) controls GR translocation to the nucleus.

What's new in using platelet research? To unravel thrombopathies and other human disorders.

This review on platelet research focuses on defects of adhesion, cytoskeletal organisation, signal transduction and secretion. Platelet defects can be studied by different laboratory platelet functional assays and morphological studies. Easy bruising or a suspected platelet-based bleeding disorder is of course the most obvious reason to test the platelet function in a patient.

Mechanisms of action and targets for actual and future antiplatelet drugs.

Platelets are key players in arterial thrombosis and have become important targets in the primary and secondary prevention of atherothrombosis. Antiplatelet drugs are primarily directed against platelets and inhibit platelet activation by a number of different mechanisms. They are used for the prevention and treatment of thrombotic processes, especially in the arterial vascular system.

The TUBB1 Q43P functional polymorphism reduces the risk of cardiovascular disease in men by modulating platelet function and structure.

The discoid form of platelets is maintained by a marginal band of tightly coiled microtubules. beta1-tubulin is the major isoform within platelet and megakaryocyte microtubules. In 24.

The pituitary adenylate cyclase-activating polypeptide is a physiological inhibitor of platelet activation.

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide of the vasoactive intestinal peptide/secretin/glucagon superfamily. Studies in two related patients with a partial trisomy 18p revealed three copies of the PACAP gene and elevated PACAP concentrations in plasma. The patients suffer from severe mental retardation and have a bleeding tendency with mild thrombocytopenia, and their fibroblasts show increased PACAP mRNA levels.

Functional polymorphisms in the paternally expressed XLalphas and its cofactor ALEX decrease their mutual interaction and enhance receptor-mediated cAMP formation.

The paternally expressed extra-large stimulatory G protein gene (XLalphas) is a splice variant of the stimulatory G-protein gene (Gsalpha) consisting of XL-exon1 and exons 2-13 of Gsalpha. A second open reading frame (ORF) in XL-exon1, that completely overlaps the XL-domain ORF, encodes ALEX, which is translated from the XLalphas mRNA and binds the XL-domain of XLalphas. We previously demonstrated that a paternally inherited functional polymorphism in XL-exon1, consisting of a 36 bp insertion and two nucleotide substitutions, is associated with Gs hyperfunction in platelets, leading to an increased trauma-related bleeding tendency and is accompanied by neurological problems and brachydactyly in two families.