Thesis (PhD (Biomedical Sciences))--University of Stellenbosch, 2010. / Bibliography / ENGLISH ABSTRACT: Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac muscle disorder worldwide. The disease is characterized by extreme variability in the amount of hypertrophy that develops in different patients in response to sarcomeric protein-encoding gene mutations. The underlying defect in HCM is altered contractility of the sarcomere, primarily due to a defective sarcomere. Although numerous disease-causing genes have been identified for HCM, the factors that modify the amount of hypertrophy that develops in a given person are still unknown, it can be hypothesized that molecules that affect contractility can act as modifiers of the hypertrophic signal, and therefore influence the development of hypertrophy. Cardiac contractility is regulated by dynamic phosphorylation of proteins within the sarcomere by kinases such as cAMP-activated protein kinase A (PKA). Because speed and energy efficiency of cardiac muscle contraction has to be regulated in order to match the body’s needs, PKA is anchored close to its targets by A-kinase anchoring proteins (AKAPs) to enable spatio-temporal control of phosphorylation. Cardiac myosin binding protein-C (cMyBPC) and cardiac troponin I (cTNI) are HCM-causing sarcomeric proteins which regulate contractility in response to PKA phosphorylation. In a previous study, our laboratory identified a phosphodiesterase 4D-interacting protein as ligand of the N-terminal of cMyBPC via a yeast-two-hybrid (Y2H) cardiac library screen. This protein is also known in the literature as myomegalin (MMGL) isoform 4. Because phosphodiesterases and PKA are sometimes anchored by the same anchoring protein (AKAP), we hypothesized that MMGL isoform 4 acts as an AKAP by anchoring PKA to the phosphorylatable N-terminal of cMyBPC, and tested this by direct protein-protein interaction analyses in a yeast-based system. The MMGL cDNA was cloned into a bait vector, which was directly assessed for interaction with two distinct PKA regulatory-subunit preys. We further investigated the function of MMGL itself by using the Y2H bait to screen a cardiac cDNA library for novel MMGL interactors. All the prey clones identified via these Y2H analyses were subsequently sequenced to determine their identity. Based on their identities and subcellular localization, all putative Y2H MMGL-prey interactions were further assessed by additional, separate biochemical techniques viz. in vivo co-immunoprecipitation and in vivo 3D co-localization. The interactions between MMGL and its known PKA-phosphorylatable sarcomeric ligands were also investigated under conditions of β-adrenergic stress, by quantitatively measuring levels of co-localization before and upon addition of the β-adrenergic agonist isoproterenol. Furthermore, in order to evaluate the role of MMGL in cMyBPC phosphorylation, we assessed the expression of the different phosphorylation isoforms of cMyBPC, with and without β-adrenergic stimulation, in the context of siRNA-mediated MMGL knockdown. We further hypothesized that MMGL and PKA may serve as modifiers of the hypertrophic phenotype. This was tested by conducting a single nucleotide polymorphism (SNP) genotyping study of the genes encoding MMGL and the regulatory subunits of PKA viz. PDE4DIP, PRKAR1A and PRKAR2A, respectively, and comparing genotypic data with clinical phenotypic traits in a family-based association study. A panel of 353 individuals, including genetically and clinically affected as well as unaffected HCM individuals, was identified. All these individuals were screened for the presence or absence of all three South African HCM founder mutations, and blood was collected and DNA extracted. Genotypes at multiple SNPs in each gene were determined by subjecting the DNA samples to TaqMan® allelic discrimination technology. Statistical analysis using quantitative transmission disequilibrium testing (QTDT) was done in order to establish whether the difference in genotype in these three genes might have an effect on HCM phenotype. Our results showed that MMGL interacted with both PKA regulatory subunits as well as with other cardiac proteins that are PKA targets, including the sarcomeric protein cTNI. It was confirmed that two regulatory subunits of PKA (PRKAR1A and PRKAR2A), cardiac ankyrin repeat protein (CARP), copper metabolism gene MURR1 domain 4 (COMMD4), α-enolase (ENO1), β-enolase (ENO3) and cTNI are novel interactors of MMGL. In order to classify a protein as an AKAP, interaction with one of PKA’s regulatory subunits are prerequisite; MMGL showed interaction with both, confirming our hypothesis of MMGL being an AKAP, moreover, classifying it as a novel dual-specific sarcomeric AKAP. The identities of the AKAPs involved in the phosphorylation of cMyBPC and cTNI had been unknown; our results indicate that MMGL is the AKAP involved in the phosphorylation of both these PKA targets. We also showed that quantitatively more interaction occurs between MMGL and its sarcomeric ligands cMyBPC and cTNI under β-adrenergic stress. This implicates that under elevated cAMP levels, PKA is dynamically recruited by MMGL to the PKA targets cMyBPC and cTNI, presumably to mediate cardiac stress responses and leading to increased cardiac contractility. Furthermore, siRNA-mediated knockdown of MMGL lead to a reduction of cMyBPC levels under conditions of β-adrenergic stress, indicating that MMGL-assisted phosphorylation is requisite for protection of cMyBPC against proteolytic cleavage. The SNP modifier study indicated that one variant in PDE4DIP (rs1664005) showed strong association with numerous clinical hypertrophy traits, including maximal interventricular septum thickness, as well as a number of other composite score traits. Two variants in PRKAR1A (rs11651687 and rs3785906) also showed strong association with some of these clinical hypertrophy traits. These results therefore suggest that variants in these two genes may act as modifiers of the HCM phenotype. In conclusion, this study ascribes a novel function to MMGL isoform 4: it meets all criteria for classification as an AKAP and appears to be involved in the phosphorylation of cMyBPC as well as cTNI; hence MMGL is likely to be an important component in the regulation of cardiac contractility, and by extension, in the development of hypertrophy. This has further implications for understanding the patho-aetiology of mutations in cMyBPC and cTNI, and raises the question of whether MMGL might itself be considered a candidate HCM-causing factor. / AFRIKAANSE OPSOMMING: Hipertrofiese kardiomiopatie (HKM) is die mees algemeenste oorerflike hartspier siekte wêreldwyd. Die siekte word gekenmerk deur die uiterste variasie in die hoeveelheid hipertrofie wat in verskillende pasiënte ontwikkel as gevolg van sarkomeriese proteïen-koderende mutasies. Die onderliggende gebrek in HKM is geaffekteerde kontraktiliteit van die sarkomeer, hoofsaaklik as gevolg van ‘n gebrekkige sarkomeer. Alhoewel daar verskeie siekte-veroorsakende gene vir HKM geïdentifiseer is, bly die faktore wat die hoeveelheid hipertrofie in ‘n gegewe persoon modifiseer, onbekend. Daar kan dus gehipotiseer word dat molekules wat kontraktiliteit beïnvloed as modifiseerders van die hipertrofiese sein kan optree, en dus die ontwikkeling van hipertrofie beïnvloed. Hartspier kontraktiliteit word gereguleer deur die dinamiese fosforilasie van proteïene binne die sarkomeer deur kinases soos bv. cAMP-geaktiveerde proteïen kinase A (PKA). Die spoed en energie doeltreffendheid van hartspier kontraksie moet gereguleer word om by die liggaam se behoeftes aan te pas; dus word PKA naby sy teikens deur A-kinase anker proteïene (AKAPs) geanker om sodoende die beheer van fosforilasie beide in die korrekte area sowel as tydsduur te reguleer. Kardiale miosien-bindingsproteïen C (cMyBPC), asook kardiale troponien I (cTNI), is beide HKM-veroorsakende sarkomeriese proteïene wat kontraktiliteit beheer deur middel van fosforilasie deur PKA. In ‘n vorige studie in ons laboratorium is ‘n fosfodiesterase 4D-interaksie proteïen as bindingsgenoot van die N-terminaal van cMyBPC geïdentifiseer deur middel van ‘n gis-twee-hibried (G2H) kardiale biblioteek sifting. In die literatuur staan dié proteïen ook bekend as miomegalin (MMGL) isovorm 4. Fosfodiesterases en PKA word soms deur dieselfde anker proteïen (AKAP) geanker, dus het ons hipotiseer dat MMGL isovorm 4 ook as AKAP kan optree deur PKA aan die fosforileerbare N-terminaal van cMyBPC te anker. Die hipotese is getoets deur middel van direkte proteïen-proteïen interaksie analises in ‘n gis-gebaseerde sisteem. Die MMGL cDNA was in ‘n jag-plasmied gekloneer, wat toe direk ge-evalueer is vir interaksie met twee verskillende PKA regulatoriese-subeenheid prooi-plasmiede. Die funksie van MMGL self is verder ondersoek deur die G2H jag-plasmied te gebruik om ‘n kardiale cDNA biblioteek te sif, sodoende om nuwe MMGL bindingsgenote te identifiseer. Alle prooi klone wat deur dié G2H analises geïdentifiseer is, was daarna onderworpe aan DNA-volgorde bepaling om hul identiteit vas te stel. Afhangende van hul identiteite en subsellulêre lokalisering, is alle moontlike G2H MMGL-prooi interaksies verder ge-evalueer deur bykomende, afsonderlike biochemiese tegnieke viz. in vivo ko-immunopresipitasie asook in vivo 3D ko-lokalisering. Die interaksie tussen MMGL en sy bekende PKA-gefosforileerde sarkomeriese bindingsgenote was ook ondersoek onder kondisies van β-adrenergiese stres, deur kwantitatief die vlakke van ko-lokalisering te meet voor en na byvoeging van die β-adrenergiese agonis isoproterenol. Om verder die rol van MMGL in cMyBPC fosforilasie te ondersoek, het ons die uitdrukking van die verskillende fosforilasie isovorms van cMyBPC, met en sonder β-adrenergiese stimulasie, in die konteks van siRNA-bemiddelde MMGL uitklop, bepaal. Ons het verder hipotiseer dat MMGL en PKA as modifiseerders van die hipertrofiese fenotipe mag dien. Dit is getoets deur ‘n enkel nukleotied polimorfisme (SNP) genotiperings studie van die gene wat kodeer vir MMGL en die regulatoriese subeenhede van PKA, viz. PDE4DIP, PRKAR1A en PRKAR2A, en daarna dié genotipiese data met kliniese fenotipiese data te vergelyk in ‘n familie-gebaseerde assosiasie studie. ‘n Paneel van 353 individue wat genetiese en klinies geaffekteerde, sowel as ongeaffekteerde HKM individue insluit, was geidentifiseerd. Alle individue was ondersoek vir die aanwesigheid of afwesigheid van al drie Suid-Afrikaanse HKM stigter mutasies; bloedmonsters is gekollekteer en DNA uitgetrek. Die genotipes van veelvoudige SNPs in elke geen was bepaal deur die DNA monsters aan TaqMan® alleliese diskriminasie tegnologie met behulp van die ABI TaqMan® Validated SNP Genotyping Assays sisteem te analiseer. Statistiese analises deur middel van kwantitatiewe transmissie disekwilibrium toetse (QTDT) was gedoen om te bepaal of die verskil in genotipe in hierdie drie gene ‘n effek op HKM fenotipe het. Ons resultate het gewys dat MMGL interaksie toon met beide PKA regulatoriese subeenhede, sowel as met ander kardiale proteïene wat ook PKA teikens is, insluitende die sarkomeriese proteïen cTNI. Dit is bevestig dat die twee regulatoriese subeenhede van PKA (PRKAR1A en PRKAR2A), kardiale ankyrin herhaal proteïen (CARP), koper metabolisme geen MURR1 domein 4 (COMMD4), α-enolase (ENO1), β-enolase (ENO3) en cTNI almal nuwe bindingsgenote van MMGL is. ‘n Proteïen moet interaksie met een van die regulatoriese subeenhede van PKA toon om as AKAP geklassifiseer te word; MMGL het interaksie met beide getoon, wat ons hipotese bevestig dat MMGL ‘n AKAP is, asook dat MMGL as ‘n nuwe dubbel-spesifieke sarkomeriese AKAP geklassifiseer kan word. Die identiteite van die AKAPs wat betrokke is in die fosforilasie van cMyBPC en cTNI was onbekend tot nou; ons resultate wys dat MMGL die AKAP is wat betrokke is in die fosforilasie van beide hierdie PKA teikens. Ons wys ook dat daar kwantitatief meer interaksie plaasvind tussen MMGL en sy sarkomeriese bindingsgenote cMyBPC en cTNI onder kondisies van β-adrenergiese stres. Dit impliseer dat PKA dinamies verwerf word deur MMGL, onder verhoogde vlakke van cAMP, tot by die PKA teikens cMyBPC en cTNI, moontlik om kardiale stres-response te bemiddel en dus te lei na verhoogde spierkontraksie. Verder het siRNA-bemiddelde uitklop van MMGL gelei na ‘n vermindering van cMyBPC vlakke onder kondisies van β-adrenergiese stres. Dit dui aan dat fosforilasie deur middel van MMGL-bystand ‘n voorvereiste is vir beskerming van cMyBPC teen proteolise. Die SNP modifiseerder studie het gewys dat een variant in PDE4DIP (rs1664005) sterk assosiasie toon met verskeie kliniese hipertrofie kenmerke, insluitende maksimale interventrikulêre septum diktheid, sowel as ander van die saamgestelde telling kenmerke. Twee variante in PRKAR1A (rs11651687 en rs3785906) het ook sterk assosiasie getoon met verskeie van die kliniese hipertropfie kenmerke. Hierdie resultate dui dus daarop dat variante in hierdie twee gene as modifiseerders van die HKM fenotipe mag optree. In samevatting skryf hierdie studie ‘n nuwe funksie aan MMGL isovorm 4 toe: dit voldoen aan alle vereistes om as AKAP geklassifiseer te word en dit blyk of dit betrokke is in die fosforilasie van cMyBPC en cTNI; dus is MMGL waarskynlik ‘n belangrike komponent in die regulasie van hartspier sametrekking, en dus met uitbreiding, in die ontwikkeling van hipertrofie. Dit hou verdere implikasies in om die siekte-oorsaak van mutasies in cMyBPC en cTNI te verstaan, en stel die vraag of MMGL self as ‘n kandidaat HKM-veroorsakende geen kan beskou word. / Medical Research Council / University of Stellenbosch / Prof Paul van Helden

Thesis (PhD ) -- Stellenbosch University, 2011. / Bibliography / ENGLISH ABSTRACT: The regulation of cardiac contractility is dependent on cooperative interaction between the thick and thin filaments, as well as their accessory proteins, within the cardiac sarcomere. Alteration in cardiac contractility due to a defective sarcomere typically results in cardiomyopathies, such as hypertrophic cardiomyopathy (HCM). One of the sarcomeric genes frequently mutated and which accounts for the second most common form of HCM encodes cardiac myosin binding protein C (cMyBPC), a thick filament accessory protein whose physiological function is poorly understood. However, studies have implicated cMyBPC in thick filament structure and function as well as in the regulation of contractility. The N-terminal region of cMyBPC houses the cMyBPC-motif, which contains three phosphorylation sites, between domains C1 and C2. The hierarchical phosphorylation of this motif, by first calcium/calmodulin kinase II (CamKII) and then by cyclic AMP-activated protein kinase (PKA), is cardinal in the role of cMyBPC in the regulation of cardiac contractility in response to ß-adrenergic stimulation. Moreover, phosphorylation of this motif is inversely correlated to cMyBPC proteolysis and has been shown to be cardioprotective. Thus, proteins that have an effect on cMyBPC function or turnover may also influence filament structure and hence affect contractility, which, in turn, affects the structure of the cardiac muscle. One such protein is the Copper metabolism MURR1-domain containing protein 4 (COMMD4), which was previously identified as a novel interactor of cMyBPC during a yeast two-hybrid (Y2H) library screen in our laboratory. COMMD4 binds specifically to the cMyBPC motif in a phosphorylation-dependent manner. The exact function of COMMD4 is unknown; however, it is a member of the COMM family of proteins that has been linked to copper metabolism as well as to the ubiquitin-proteasome pathway (UPS). Intriguingly, recent studies have shown that the UPS plays a role in cMyBPC-derived HCM, while dietary copper depletion is also known to cause cardiac hypertrophy. Based on these findings, COMMD4 was considered an interesting candidate regulator of sarcomeric function and contractility, and by extension, a candidate modifier of cardiac hypertrophy. Thus, the aim of the present study was two-fold. Firstly, COMMD4 was used as bait in a Y2H library screen to determine its distal ligands, with a view to further elucidate its function, particularly in the context of MyBPC functioning, and identified interactors were subjected to further in vitro and in vivo verification studies. Also, the phosphorylation-dependent nature of the interaction between COMMD4 and cMyBPC was further investigated using a domain/phosphorylation assay. Secondly, COMMD4 and its Y2H-identified putative interactors were assessed as possible modifiers of hypertrophy in a family-based association study, using three cohorts of South African HCM-families in which one of three founder mutations segregate. Six putative interactors, viz. cardiac actin (ACTC1), Down syndrome critical region 3 (DSCR3), enolase 1 (ENO1), F-box and leucine rich repeat protein 10 (FBXL10), legumain (LGMN) and sorting nexin3 (SNX3) were identified and confirmed as COMMD4 interactors using Y2H analyses, followed by in vitro and in vivo co-immunoprecipitation and 3D co-localisation assays. Moreover, as some COMMD protein family members and the newly-identified interactors of COMMD4 have previously been linked to the UPS, the functional effect of siRNA-mediated knockdown of COMMD4 on cMyBPC turnover was also investigated. Data revealed accumulation of cMyBPC in the endosomes upon COMMD4 knockdown, suggesting a functional role for COMMD4 in the turnover of cMyBPC. In addition, association analysis revealed strong evidence of association between various single nucleotide polymorphisms (SNPs) in SNX3 and a number of hypertrophy traits, thus suggesting a role for SNX3 as a candidate modifier of hypertrophy in HCM. No evidence of association was observed for any of the genes encoding the other COMMD4 interactors implicated in protein turnover. The present study demonstrates that COMMD4, a little understood member of the COMM family of proteins, binds to the cMyBPC motif of cMyBPC in a phosphorylation-dependent manner. Furthermore, based on the functions of its protein interactions, we hypothesise that COMMD4 plays a role in protein trafficking and turnover. More specifically, COMMD4 seems to help to facilitate formation of protein complexes with the Skp1-Cul1-Fbxl (SCF) E3 ubiquitin ligase and probably helps to stabilise the target substrate for subsequent ubiquitin-conjugation. As COMMD4 seems to affect the protein turnover of cMyBPC and possibly other sarcomeric proteins, such as actin, these results establish a novel association between the sarcomere, HCM and the UPS. In addition, identification of SNX3 as a hypertrophy modifier will allow for the improved understanding of HCM patho-aetiology. SNX3 thus adds to the growing body of sarcomeric modifier genes, which, eventually, may improve risk profiling in HCM. Furthermore, as genetic modifiers appear sufficient to completely prevent disease expression in some HCM carriers, the identification of SNX3 may point to the protein turnover pathway as a potential new target for intervention. / AFRIKAANSE OPSOMMING: Die regulering van kardiale kontraktiliteit is afhanklik van die koöperatiewe interaksie tussen die dik en dun filamente, asook hul geassosieerde proteïene, in die kardiale sarkomeer. Veranderinge in kardiale kontraktiliteit as gevolg van 'n defektiewe sarkomeer lei tot kardiomiopatieë soos hipertrofiese kardiomiopatie (HKM). Een van die sarkomeriese gene wat dikwels gemuteer is en wat verantwoordelik is vir die tweede algmeenste vorm van HKM,is dié van kardiale miosien-bindingsproteïen C (cMyBPC),'n proteïen geassosieer met die dik filament waarvan die fisiologiese funksie nog nie goed bekend is nie. Studies betrek cMyBPC in dik filament struktuur en funksie asook in die regulering van kontraktiliteit. Die N-terminale gebied van cMyBPC huisves die cMyBPC-motief, wat drie fosforilerings-setels tussen domeine C1 en C2 bevat. Die hiërargiese fosforilering van hierdie motief, eerstens deur kalsium/kalmodulien-gereguleerde kinase II (CamKII), gevolg deur siklies AMP-geaktiveerde proteïen kinase (PKA), is kardinaal in die rol van cMyBPC in die regulering van kardiale kontraktiliteit in reaksie op ß-adrenergiese stimulasie. Verder, fosforilering van hierdie motief is omgekeerd gekorreleer aan cMyBPC proteolise en is ook bewys om kardiobeskermend te wees. Dus, proteïene wat 'n uitwerking het op die funksie van cMyBPC mag ook filament struktuur en kontraktiliteit beïnvloed, wat op hul beurt die struktuur van die kardiale spier affekteer. Die koper metabolisme MURR1-domein bevattende protein 4 (COMMD4), was voorheen geïdentifiseer as 'n nuwe bindingsgenoot van cMyBPC tydens gis twee-hibried (G2H) analise in ons laboratorium. COMMD4 bind spesifiek aan die cMyBPC motief in 'n fosforilasie afhanklike wyse. Die presiese funksie van COMMD4 is onbekend; maar dit is 'n lid van die COMM domein familie van proteine wat geassosieerd is met koper metabolisme sowel as die “ubiquitin” proteosoom pad (UPP). Interesant genoeg, onlangse studies het bewys dat die UPP 'n rol speel in cMyBPC-afgeleide HKM, terwyl koper uitputting in die dieet ook bekend is om kardiale hipertrofie te veroorsaak. Gebaseer op hierdie bevindinge was COMMD4 oorweeg as 'n interessante kandidaat reguleerder van sarkomeries funksie en kontraktiliteit, asook 'n kandidaat modifiseerder van kardiale hipertrofie. Dus, die doel van die huidige studie was tweeledig. Eerstens, was COMMD4 as aas gebruik in 'n G2H biblioteek sifting om sy distale ligande te bepaal, met die oog om verdere lig te werp op sy funksie, veral in die konteks van MyBPC funksionering, en geïdentifiseerde bindingsgenote was onderwerp aan verdere 'in vitro’ en 'in vivo’ verifikasie studies. Daarbenewens was die fosforilering-afhanklike aard van die interaksie tussen COMMD4 en cMyBPC verder ondersoek met behulp van 'n domein/fosforilasie toets. Tweedens, COMMD4 en sy G2H-geïdentifiseerde vermeende bindingsgenote was geassesseer as moontlik modifiseerders van hipertrofie in 'n familie-gebaseerde assosiasie studie, met behulp van drie kohorte van Suid-Afrikaanse HKM-families waarin een van die drie stigter mutasies segregeer. Ses vermeende interaktors, nl. kardiale aktien (ACTC1), Down-sindroom kritiese streek 3 (DSCR3), enolase 1 (ENO1), F-boks en leusien ryke herhalings proteïen 10 (FBXL10), legumain (LGMN) en sorteer nexin3 (SNX3) is geïdentifiseer en bevestig as COMMD4 bindingsgenote deur G2H analises, gevolg deur in vitro en in vivo ko-immunopresipitasie en 3D ko-lokalisasie toetse. Die funksionele effek van siRNA-bemiddelde uitklop van COMMD4 op cMyBPC omset was ook ondersoek omdat 'n paar COMMD proteïen familielede, asook die nuut-geïdentifiseerde bindingsgenote van COMMD4, geassosieerd is met die UPP. Data toon ophoping van cMyBPC in die endosome by COMMD4 uitklop, wat dus aandui op 'n funksionele rol vir COMMD4 in die omset van cMyBPC. Daarbenewens, toon assosiasie analise sterk bewyse van assosiasie tussen die verskillende enkele nukleotied polimorfismes (SNPs) in SNX3 en 'n aantal hipertrofiese kenmerke,wat aandui op 'n rol vir SNX3 as 'n kandidaat modifiseerder van hipertrofie in HKM. Geen bewyse van assosiasie was waargeneem vir enige van die gene wat kodeer vir die ander COMMD4 bindingsgenote wat geïmpliseer word in die proteïen omset. Die huidige studie toon dat COMMD4, 'n min verstaande lid van die COMM familie van proteïene, aan die cMyBPC motief van cMyBPC in'n fosforilasie-afhanklike wyse bind. Verder, gebasseer op die funksies van die proteïen interaksies, hipotiseer ons dat COMMD4 'n rol speel in proteïen vervoer en omset. Meer spesifiek, COMMD4 blyk om die vorming van proteïene komplekse met die Skp1-Cul1-Fbxl (SCF) E3 "ubiquiti". ligase te fasiliteer en help waarskynlik om die teiken-substraat vir die daaropvolgende ubiquitin-konjugasie te stabiliseer. Omdat dit lyk asof COMMD4 die proteïen-omset van cMyBPC en moontlik ander sarkomeriese proteïene, soos aktien, ook beïnvloed, vestig die resultate dus 'n nuwe assosiasie tussen die sarkomeer, HKM en die UPP. Daarbenewens sal die identifisering van SNX3 as 'n hipertrofie modifiseerder voorsiening maak vir die verbeterde begrip van HKM pato-etiologie. SNX3 voeg dus by tot die groeiende ?getal van sarkomeriese modifiseerende gene, wat uiteindelik, die risiko-ontleding in HKM mag verbeter. Verder, omdat dit blyk dat genetiese modifiseerders voldoende is om die siekte-uitdrukking heeltemal te verhoed in sekere HKM draers, kan die identifikasie van SNX3 na die proteïen-omset roete dui as 'n potensiële nuwe teiken vir intervensie.