Ritka öröklött és szerzett haemorrhagiás diathesisek molekuláris elemzése, a rendellenességek strukturális és funkcionális következményei = Molecular evaluation of rare inherited and acquired bleeding diatheses, structural and functional consequences of the disorders

Ritka trombocita funkcios zavarok es koagulopatiak vizsgalata molekularis genetikai es feherje szinten. Az alabbiakban a projekt harom legfontosabb eredmenyet soroljuk fel: 1/Ket uj mutacionak a felfedezese a trombocita glikoprotein (GP) IIb-ben, melyek II-es tipusu Glanzmann thrombastheniat okoztak. A mutans feherjek transzfektalt sejtekben tortenő analizise ravilagitott: a) a "thigh" domen szerepere a GPIIIa-val valo komplex kepződesben, b) a "calf-2" domen fontosagara a feherje eresi folyamataban es intracellularis vandorlasaban. 2/ A factor X (FX) genjeben bekovetkezett homozigota c.730G>A/p.Gly204Arg mutacio kovetkezteben a FX antigen hianyat eszleltuk egy sulyos verzekenysegben szenvedő gyermekben. Az aminosav csere destabilizalta a FX ket lancat osszetarto diszulfid hidat. A mutans feherje elterul a normalis szekrecios uttol, megakad a transz Golgi-keső endoszoma szinten, s igy nem szekretalodik. 3/ Egy SLE-ben szenvedő betegen eletet veszelyeztető verzes alakult ki. A beteg vizsgalata a szerzett faktor XIII (FXIII) deficiencia egy uj, eddig nem leirt formajanak a felismeresehez vezetett. A beteg plazmajaban FXIII aktivitas, FXIII komplex, FXIII A es B alegyseg antigen nem volt kimutathato, mig trombocitakban a FXIII aktivitas es FXIII-A antigen normal volt. A sulyos verzest egy autoantitest okozta, mely a komplexben levő es szabad FXIII-B-hez egyarant kotődott es nagyon kifejezetten meggyorsitotta eliminaciojukat a keringesből. | Rare platelet function disorders and coagulopathies were investigated at molecular genetic and/or protein level. Below the three most important results of the project are described: 1/ Investigation of a patient with type II Glanzmann thrombasthenia led to the discovery of two novel causative mutations in the platelet glycoprotein (GP) IIb gene. Analysis of the mutant proteins in transfected cells shed light a) on the role of thigh domain in the complex formation with GPIIIa, b) on the involvement of calf-2 domain in the maturation and intracellular trafficking of the protein. 2/ Due to a homozygous novel c.730G>A/p.Gly204Arg mutation in the factor X (FX) gene no FX antigen was found in the plasma of a child with severe bleeding diathesis. The amino acid replacement destabilized the disulfide bond that holds the two FX chains together. The mutant protein could not be secreted; it was diverted from the normal secretory pathway and retained at the trans Golgi-late endosome level. 3/ In an SLE patient with life threatening bleeding a new form of acquired factor XIII (FXIII) deficiency was discovered. The patient had undetectable FXIII activity, FXIII complex, FXIII A and B subunit antigen levels in the plasma, while in platelets FXIII activity and FXIII-A antigen level was normal. It was revealed that the patient developed an autoantibody that bound to FXIII-B both in complex and free form and highly accelerated their elimination from the circulation.