Molekularna citogenetika nekih neurorazvojnih poremećaja

Rinčić, Martina (2014) Molekularna citogenetika nekih neurorazvojnih poremećaja. PhD thesis, Sveučilište u Zagrebu.

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Abstract

Neurodevelopmental disorders encompass a large group of clinically heterogeneous, chronic disorder characterized by damage of the developing central nervous system, resulting in impaired progression of one or more developmental domains (physical, cognitive, social and emotional). Intellectual Disability (ID) and Autism spectrum disorders (ASD) are common neurodevelopmental disorders that have in common severely impaired cognitive development in early childhood and adolescence. ID is defined as below-average intellectual functioning with significant limitation in at least two domains of daily living skills. It is estimated that ID affects 1-3% of the general population. By the level of intellectual functioning ID is divided as mild (IQ 50-55), moderate (35-40 / 50-55), severe (20-25 / 35-40), deep (below 20/25), and the ID of indefinite severity. Mild/moderate form of ID occurs 7-10 times more often than the heavier degrees, and it is estimated that comprises 80-85% of all patients with ID. ASD as a diagnostic category encompasses a wide range of disorders of early childhood marked by major deviations in social interaction, social communication/imagination and motor skills that are reflected in stereotypical movements and interests. According to current research, it is estimated that the prevalence of ASD is 62/10000, and occurs four times more often in boys than girls. Etiological diagnosis in patients with ID is identified in 40-60% of cases. However, the etiology of mild ID that occurs 7-10 times more frequently than moderate and severe form is known only in about 24% of cases. Genetic factors are found in 30% of all cases of ID and they represent more than 60% of all known causes. Etiology of ASD is extremely heterogeneous and includes genetic factors, epigenetic modifications of the genome and environmental impact. Genetic factors that represent most of the known etiology (10-20%) can be different, but none of them covers more than 1-2% of all cases of ASD. It is believed that genetic factors underlay the large number of undiagnosed cases of ID and ASD given that until recently sufficiently sensitive screening technique were not available. The study was conducted on 379 subjects. Considering the referral diagnosis, subjects where divided into two groups: 355 diagnosed with ID and 24 diagnosed with ASD. In this research, comprehensive genetic analysis was conducted to determine the etiological diagnosis and to identify candidate genes underlying ID and ASD. By use of classical chromosome analysis (GTG - G-bands by Trypsin using Giemsa) chromosomal aberrations where identify in 5% of patients diagnosed with ID, while the percentage of detected abnormalities in patients diagnosed with ASD was 12.5%. In patients with normal findings of GTG analysis, further molecular cytogenetic analysis was conducted using MLPA (Multiplex ligation dependent probe amplification) and aCGH (Array comparative genomic hybridization) techniques. Combining different MLPA probe sets, submicroscopic chromosomal aberrations were detected in a further 10.3% of patients diagnosed with ID, while MLPA analysis of patients diagnosed with ASD revealed no aberrant results. Subjects with normal findings of GTG and MLPA analysis where further analyzed by aCGH technology. Pathogenic chromosomal aberrations were detected in 7% of patients diagnosed with ID, and in 21% of patients diagnosed with ASD. Bioinformatic analysis of aCGH data obtained in this study revealed a potential candidate genes underlying ID and ASD (ARHGAP8, ATRNL1, ATXN10, B3GALT6, C12orf5, CASKIN1, CLASP2, CNKSR2, CNTN6, CNTNAP2, CRHR2, CSMD2, DDR1, DST, EVC, FBLN1, FRG1, FTSJ1, FXN, GPHB5, GPRIN2, HS6ST2, IQSEC3, KIAA0513, KIAA1267, LANCL2, MACROD2, MAGEA8, MAGI2, NBPF1, NPAS1, NR1D2, NUP50, PDZD2, PLEKHA5, PPP1R14C, PPP1R18, PPP2R5E, PRODH, PTPRT, RTN4R, SNPH, SYP, TFG, TPPP, VARS2, WDR45, WIPF1, WNT7A). Classical chromosome analysis by GTG banding showed a lower percentage of aberrations detected compared with molecular cytogenetic techniques (MLPA and aCGH). In this study combination of classical and molecular cytogenetic techniques revealed a greater number of submicroscopic aberrations underlying RIP and ASD. Also some new potential candidate genes underlying ID and ASD where identified. Conducted research indicates that molecular cytogenetic techniques allow screening of the genome in neurodevelopmental disorders from genotype to phenotype, which facilitates defining new genetic syndromes.

Abstract in Croatian

Neurorazvojni poremećaji obuhvaćaju veliku grupu, klinički heterogenih, kroničnih poremećaja koje karakterizira oštećenje razvoja središnjeg živčanog sustava, što za posljedicu ima narušeno napredovanje u jednoj ili više razvojnih domena (tjelesna, kognitivna/spoznajna, socijalna i emocionalna). Razvojni intelektualni poremećaj (RIP, engl. Intellectual disability) i poremećaji autističnog spektra (engl. Autism spectrum disorders, ASD) predstavljaju česte neurorazvojne poremećaje kojima je zajedničko teško oštećenje kognitivnog razvoja u ranoj dječjoj dobi i adolescenciji. RIP se definira kao ispodprosječno intelektualno funkcioniranje uz značajna ograničenje u najmanje dvije vještine svakodnevnog života. Procjenjuje se da RIP zahvaća 1-3% opće populacije. Prema razini intelektualnog funkcioniranja RIP se djeli na: blagi (IQ 50 – 55), umjereni (35-40/50-55), teški (20-25/ 35-40), duboki (ispod 20/25), te RIP neodređene težine. Laki/blagi oblik RIP-a javlja se 7-10 puta češće od težih stupnjeva, te se procjenjuje da obuhvaća 80-85% svih osoba s RIP-om. ASD kao dijagnostička kategorija obuhvaća širok spektar poremećaja rane dječje dobi obilježenih velikim odstupanjima u socijalnim interakcijama, socijalnoj komunikaciji i imaginaciji te motoričkim vještinama koje se očituju u sterotipijama. Prema današnjim istraživanjima procjenjuje se da prevalencije ASD-a iznosi 62/10000, a javlja se 4 puta češće kod dječaka u odnosu na djevojčice. Etiološka dijagnoza u osoba s RIP-om identificira se u 40-60% slučajeva. Međutim etiologija blagog RIP-a koji se javlja 7-10 puta češće od umjerenog i teškog, poznata je tek u oko 24% slučajeva. Genetski faktori nalaze se u podlozi 30% svih slučajeva RIP-a, te predstavljaju više od 60% svih poznatih uzroka. Poremećaji autističnog spektra imaju izrazito heterogenu etiologiju koja obuhvaća genetske faktore, epigenetske modifikacije unutar genoma te utjecaj okoline. Genetski faktori koji predstavljaju najveći dio poznate etiologije (10-20%) mogu biti različiti, međutim niti jedan od njih ne obuhvaća više od 1-2% svih slučajeva ASD-a. Unatoč ekstenzivnim istraživanjima, etiologija RIP-a i ASD-a u velikom broju slučajeva ostaje nepoznata. Smatra se da se genetski faktori nalaze u podlozi velikog broja nedijagnosticiranih slučajeva RIP-a i ASD-a obzirom da do nedavno nisu bile dostupne dovoljno osjetljive tehnike skrininga. Istraživanje je provedeno na 379 ispitanika podijeljenih u dvije skupine obzirom na uputnu dijagnozu. 355 ispitanika s uputnom dijagnozom RIP i 24 ispitanika s uputnom dijagnozom ASD. Istraživanjem je povedena sveobuhvatna genetska analiza s ciljem utvrđivanja etiološke dijagnoze i identifikacije gena kandidata u podlozi RIP-a i ASD-a. Klasičnom analizom kromosoma GTG prugama (GTG engl. G-bands by Trypsin using Giemsa) kod 5% ispitanika s dijagnozom RIP-a utvrđene su kromosomske aberacije, dok je postotak detektiranih aberacija kod ispitanika s dijagnozom ASD-a iznosio 12,5%. Kod ispitanika s urednim nalazom GTG pruganja provedena je daljnja molekularno citogenetska analiza MLPA (MLPA engl. multiplex ligation dependent probe amplification) i aCGH (aCGH engl. array comparative genomic hybridization) tehnikama. Kombinacijom MLPA setova proba detektirane su submikroskopske kromosomske aberacije u daljnjih 10,3% ispitanika s dijagnozom RIP-a, dok MLPA analiza ispitanika s dijagnozom ASD-a nije pokazala aberantne rezultate. Daljnjom obrada aCGH tehnikom ispitanika s urednim nalazom GTG i MLPA analiza patogene kromosomske aberacije detektirane su kod 7% ispitanika s dijagnozom RIP-a, te u 21% ispitanika s dijagnozom ASD-a. Bioinformatičkom analizom aCGH podataka dobivenih ovim istraživanjem otkriveni su potencijalni geni kandidati u podlozi RIP-a i ASD-a (ARHGAP8, ATRNL1, ATXN10, B3GALT6, C12orf5, CASKIN1, CLASP2, CNKSR2, CNTN6, CNTNAP2, CRHR2, CSMD2, DDR1, DST, EVC, FBLN1, FRG1, FTSJ1, FXN, GPHB5, GPRIN2, HS6ST2, IQSEC3, KIAA0513, KIAA1267, LANCL2, MACROD2, MAGEA8, MAGI2, NBPF1, NPAS1, NR1D2, NUP50, PDZD2, PLEKHA5, PPP1R14C, PPP1R18, PPP2R5E, PRODH, PTPRT, RTN4R, SNPH, SYP, TFG, TPPP, VARS2, WDR45, WIPF1, WNT7A). Klasična analiza kromosoma GTG pruganjem u provedenom istraživanju pokazale je niži postotak detekcije aberacija u usporedbi s molekularno citogenetskim tehnikama (MLPA i aCGH). Upotrebom recentnih tehnika otkriven je veći broj submikroskopskih aberacija u podlozi RIP-a i ASD te su utvrđeni novi potencijalni geni kandidati. Provedeno istraživanje ukazuje da molekularno citogenetske tehnike skrininga genoma omogućavaju analizu neurorazvojnih poremećaja od genotipa prema fenotipu, što danas olakšava definiranje novih genetskih sindroma.

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