A study of the genetic etiology of nonsyndromic cleft lip and palate
Date
2011-12-23
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Abstract
Huule- ja/või suulaelõhe on üks sagedasemaid kaasasündinud väärarenguid, esinemissagedusega 1/700 elussünni kohta, sõltuvalt geograafilistest ja etnilistest variatsioonidest. Huule- ja suulalelõhede kliinilisi klassifikatsioone on erinevaid kuid üldiselt jaotatakse lõhed kaheks suureks haigusfenotüübiks: huule ja/või suulalelõhe (CL/P) ja suulaelõhe (CP). Suulõhede tekkes mängivad olulist rolli keskonna- ja geneetilised tegurid ning elustiiliga seotud riskifaktorid. Sündroomsete suulõhedega seostatud geenide uuringud on näidanud nende olulisust ka mittesündroomsete suulõhede etioloogias. Geneetiliste tegurite olulisus mittesündroomse suulõhe tekkes on kinnitust leidnud perekondade ja kaksikute uuringutes. Kandidaatgeenide uurimisel põhinevad assotsiatsiooniuuringute ja aheldusanalüüside tulemused erinevates populatsioonides on varieeruvad ja vähene kokkulangevus on põhjustatud geneetilisest heterogeensusest ja väikesest uuringute võimsusest.
Suulõhega sündinud lapsed vajavad ravi erinevate spetsialistide poolt ja seda erinevates vanuseperioodided sünnist kuni täiskasvanuks saamiseni ning tihti ka kauem. Suulõhe diagnoos ei ole eluohtlik, kuid neil lastel on kahjustatud paljud olulised funktsioonid nagu: imemine, kõne, keskkõrva ventilatsioon, kuulmine, hingamine ning häirunud on ka näo- ja lõualuude süsteemi areng ning kasv. Need probleemid omakorda võivad põhjustada emotsionaalset stressi, psühholoogilisi probleeme ning võivad mõjutada lapse hakkama saamist koolis. Rehabilitatsioon on võimalik hea meeskonnatööga erinevate spetsialistide vahel ning heas koostöös lapse perekonnaga. Pikka aega kestev ravi on ühiskonnale ka kulukas.
Kuna mittesündroomsete suulõhede etioloogia on multifaktoriaalne, siis väga tihti on raske leida tekkepõhjust, ometi ennetustöö ja inimeste teadlikuse tõstmine võib vähendada lõhega sündinud laste arvu. Suulõhede riskifaktorite teadvustamine ja kaardistamine on esimene samm ennetustöös. Genotüübi ja fenotüübi uuringud võivad tuua uusi teadmisi lähiajal, aga selleks on vaja suuri mitmete keskuste koostöös toimuvaid uuringuid, mis leiaksid seoseid nii keskonnategurite kui ka geneetiliste riskifaktorite vahel.
Eestis puudub riiklik statistika suulõhedga laste sündivuse osas. Huule- ja/või suulaelõhede esmased lõikused tehakse kahes Eesti suurimas haiglas: SA Tartu Ülikooli Kliinikumis ja Põhja-Eesti Regionaalhaiglas. Juhul kui suulõhega lapse vanemad otsustavad pöörduda mujale (välisriiki), siis ei ole võimalik juhtu dokumenteerida.
Käesoleva doktoritöö eesmärgiks oli:
• Ülevaate saamine SA Tartu Üliooli Kliinikumis ravitud suulõhedest ajavahemikul 1910-2000.
• Huule- ja suulaelõhede teket põhjustavate epidemioloogiliste tegurite ja nende esinemise seaduspärasuste leidmine.
• Ananlüüsida kraniofatsiaalses morfogeneesis ja/või patogeneesis osalevate kandidaatgeenide võimalikku seost mittesündroomse CL/P ja CP Eesti ja Kirde-Euroopa (Eesti, Läti, leedu) uuringurühmas.
Valitud geenidega teostati ühenukleotiidse polümorfismi (SNP) case-control assotsiatsioonanalüüsid nii Eesti uuringurühmas kui ka Eesti, Läti ja Leedu ühendatud Kirde-Euroopa uuringurühmas eraldi CL/P ja CP fenotüübiga patsientidel.
Uurimistöö olulisemad tulemused võib kokku võtta järgmiselt:
• Leidsime suure suulaelõhede esinemissageduse (CL : CLP : CP – 1 : 2 : 2), mis on sarnane Soomes ja Rootsis tehtud uuringutega ja mille põhjused vajavad edaspidist uurimist.
• Antud uuring on esimene, kus me näitasime, et FGF1 geeni järjestuse variandid on seotud mittesündroomse CL/P geneetilise eelsoodumusega; ning leidsime kinnitust et TIMP2 ja WNT9B geenide järjestuse variandid on seotud CL/P geneetilise eelsoodumusega Kirde-Eesti populatsioonis.
• Antud uuringu käigus leidsime kinnitust, et teiste populatsioonide uuringutest leitud FOXE1 geenide järjestuse variandid on seotud CL/P geneetilse eelsoodumusega Kirde-Euroopa pupulatsioonis (Eesti, Läti, Leedu).
• Antud uuringus ei leidnud kinnitust kirjanduses erinevates populatsioonides kõige rohkem mainitud ja CL/Pga kandidaatgeenina seostatud IRF6 geenide järjestuse variantide seos CL/Pga Eesti populatsioonis. Antud leidu võib seletada geneetilise heterogeensusega.
• MSX1 ja MTHFR geenide järjestuse variandid on seotud mittesündroomse CL/P geneetilise eelsoodumusega Eesti populatsioonis.
• Leidsime tõendeid, et OFC3 lookus, kromosoomil 19q13 on tõenäoliselt seotud mittesündroomse CL/Pga.
• IRF6, COL2A1, COL11A2 and WNT3 geenide järjestuse variandid on seotud mittesündroomse CP geneetilise eelsoodumusega Kirde-Euroopa pupulatsioonis (Eesti, Läti, Leedu).
• FGF ja Wnt signaalrajad ning nendes osalevad geenid omavad olulist rolli nii CL/P kui ka CP etioloogias.
Mittesündroomse suulõhe etioloogia kätkeb endas palju erinevaid tegureid ning nende tegurite ja tegurite omavahelise koostoime uurimisega tegeletakse maailmas. Uuringute teostamise teeb raskeks huulelõhede multifaktoriaalne taust ja ka erinevate populatsioonide heterogeensus. Uuringud on näidanud erinevate kandidaatgeenide olulisust erinevates populatsioonides. Vajalik on erinevate regioonide detailne geneetiline kaardistamine haigusseoseliste variantide funktsionaalsete effektide kindlakstegemiseks rahvusvahelises koostöös erinevate uurimisrühmadega ja biopankaadega.
Cleft lip (CL), cleft lip with or without cleft palate (CL/P) and isolated cleft palate (CP), collectively termed oral clefts (OC), are the second most common birth defects among newborn. These defects arise in about 1 in 700 liveborn babies, with ethnic and geographic variation. Approximately 75% of CL/P and 50% of CP cases are isolated defects and no other deformities are found in those children. Those OCs are therefore called nonsyndromic. It has been suggested that the development of nonsyndromic OC occurs as a result of the interaction between different genetic and environmental factors. Genetic factors contributing to CL/P formation have been identified for some syndromic cases, but knowledge about genetic factors that contribute to nonsyndromic CL/P is still unclear. The high rates of familial occurrences, risk of recurrence, and elevated concordance rates in monozygotic twins provide evidence for a strong genetic component in nonsyndromic CL/P. The identification of the genes responsible for diseases has been a major focus of human genetics over the past 40 years. The introduction of modern molecular methods, experimental animal knockout models and advances in the technique of gene mapping have provided new candidate genes for orofacial clefting, both for syndromic and nonsyndromic cases. However, the results of earlier candidate-gene-based association studies, performed in different populations, have been conflicting, with only a few candidate loci being implicated in OC phenotypes. This inconsistency indicates the challenges in searching associations with a relatively rare phenotype such as nonsyndromic clefting. Although OC is usually not a life-threatening condition, many functions such as feeding, digestion, speech, middle-ear ventilation, and hearing, respiration, facial and dental development can be disturbed because of the structures involved. These problems can also cause emotional, psychosocial and educational difficulties. Affected children need multidisciplinary care from birth until adulthood. Orofacial clefts pose a burden to the individual, the family, and society, with substantial expenditure, and rehabilitation is possible with good quality care. Care for children born with these defects generally includes many disciplines – nursing, facial plastic surgery, maxillofacial surgery, otolaryngology, speech therapy, audiology, counselling, psychology, genetics, orthodontics, and dentistry. Fortunately, early and good quality rehabilitation of children with OC usually gives satisfactory outcomes. National statistics regarding orofacial clefts in Estonia was nonexistent at the start of this study. The only prevalence findings known to us were those of Lõvi-Kalnin (1996), conducted during 1970–1980. On the basis of the data from the study, the current rate of occurrence of clefts in Estonia would be 1 case per 777 live births. The only way to estimate the number of children affected by clefts is to use the pre-existing information from previous visits to maxillofacial surgeons. The main goals of the present study were: 1)To evaluate the occurrence rate of OC, on the basis of records of patients treated in the Department of Oral and Maxillofacial Surgery of the Tartu University Hospital, during the period of 1910–2000. 2) To determine the rate of occurrence between different cleft types on the basis of gender and location.3) To record the epidemiological factors which may influence the development of OC, and to evaluate their occurrence regularities. 4) To investigate the possible contribution of recognized candidate genes in the development of nonsyndromic OC in an Estonian population and in the Baltic region (Estonia, Latvia, Lithuania). The main conclusions of our work are as follows: 1) The present study is the first to present an overview of patients with clefts treated in the Department of Oral and Maxillofacial Surgery of the Tartu University Hospital over the course of 90 years (1910–2000). During this period, 583 patients were recorded (251 females and 332 males; a sex ratio of 1:1.32 respectively). 2) Of the 583 patients with OC, 19% had CL, 39% had CP and 42% had CLP. We found a high occurrence rate of CP among all clefts (CL: CLP: CP – 1:2:2). The most common OC in boys was left-side CLP; in girls it was CP. The left side of the face was damaged 2.2 times more frequently than the right side. 3) Over a third of mothers of children with OC had experienced psychological stress during pregnancy, 45% of mothers had previously undergone at least one medical abortion, and 20% of mothers had been exposed to teratogenic toxic substances. The average birthweight of the children with OC was similar to the birthweight of children without clefts. An association between maternal age and the occurrence of OC could not be observed. 4) The results of this study suggest that several genes known to be involved in craniofacial morphogenesis and/or palatogenesis, may contribute to the incidence of OC. 4.1. Our data provide additional confirmation for the role of MSX1 and MTHFR in the etiology of nonsyndromic CL/P in the Estonian sample. 4.2 We found new supportive evidence that the orofacial clefting locus, OFC3 on Chr 19q13, is probably involved in nonsyndromic CL/P across different populations. 4.3. This study provides, for the first time, evidence of the implication of IRF6, COL2A1, COL11A2 and WNT3 in the occurrence of nonsyndromic CP in north-eastern European populations (Estonians, Latvians, Lithuanians). 4.4. We could not demonstrate convincing evidence of an association between CL/P and IRF6, the candidate gene most consistently replicated. This result could be explained by the various confounding factors and heterogeneity among the populations. 4.5. The present study is the first to demonstrate an association between CL/P and common SNPs and haplotypes in FGF1, and provides new evidence that variation in the TIMP2 and WNT9B genes contributes to nonsyndromic CL/P. 4.6. We have successfully replicated previous findings implicating FOXE1 as a susceptibility locus for CL/P across different populations. 4.7 The results of this study underline the importance of the FGF and Wnt signalling pathway genes in the etiology of both CL/P and CP.
Cleft lip (CL), cleft lip with or without cleft palate (CL/P) and isolated cleft palate (CP), collectively termed oral clefts (OC), are the second most common birth defects among newborn. These defects arise in about 1 in 700 liveborn babies, with ethnic and geographic variation. Approximately 75% of CL/P and 50% of CP cases are isolated defects and no other deformities are found in those children. Those OCs are therefore called nonsyndromic. It has been suggested that the development of nonsyndromic OC occurs as a result of the interaction between different genetic and environmental factors. Genetic factors contributing to CL/P formation have been identified for some syndromic cases, but knowledge about genetic factors that contribute to nonsyndromic CL/P is still unclear. The high rates of familial occurrences, risk of recurrence, and elevated concordance rates in monozygotic twins provide evidence for a strong genetic component in nonsyndromic CL/P. The identification of the genes responsible for diseases has been a major focus of human genetics over the past 40 years. The introduction of modern molecular methods, experimental animal knockout models and advances in the technique of gene mapping have provided new candidate genes for orofacial clefting, both for syndromic and nonsyndromic cases. However, the results of earlier candidate-gene-based association studies, performed in different populations, have been conflicting, with only a few candidate loci being implicated in OC phenotypes. This inconsistency indicates the challenges in searching associations with a relatively rare phenotype such as nonsyndromic clefting. Although OC is usually not a life-threatening condition, many functions such as feeding, digestion, speech, middle-ear ventilation, and hearing, respiration, facial and dental development can be disturbed because of the structures involved. These problems can also cause emotional, psychosocial and educational difficulties. Affected children need multidisciplinary care from birth until adulthood. Orofacial clefts pose a burden to the individual, the family, and society, with substantial expenditure, and rehabilitation is possible with good quality care. Care for children born with these defects generally includes many disciplines – nursing, facial plastic surgery, maxillofacial surgery, otolaryngology, speech therapy, audiology, counselling, psychology, genetics, orthodontics, and dentistry. Fortunately, early and good quality rehabilitation of children with OC usually gives satisfactory outcomes. National statistics regarding orofacial clefts in Estonia was nonexistent at the start of this study. The only prevalence findings known to us were those of Lõvi-Kalnin (1996), conducted during 1970–1980. On the basis of the data from the study, the current rate of occurrence of clefts in Estonia would be 1 case per 777 live births. The only way to estimate the number of children affected by clefts is to use the pre-existing information from previous visits to maxillofacial surgeons. The main goals of the present study were: 1)To evaluate the occurrence rate of OC, on the basis of records of patients treated in the Department of Oral and Maxillofacial Surgery of the Tartu University Hospital, during the period of 1910–2000. 2) To determine the rate of occurrence between different cleft types on the basis of gender and location.3) To record the epidemiological factors which may influence the development of OC, and to evaluate their occurrence regularities. 4) To investigate the possible contribution of recognized candidate genes in the development of nonsyndromic OC in an Estonian population and in the Baltic region (Estonia, Latvia, Lithuania). The main conclusions of our work are as follows: 1) The present study is the first to present an overview of patients with clefts treated in the Department of Oral and Maxillofacial Surgery of the Tartu University Hospital over the course of 90 years (1910–2000). During this period, 583 patients were recorded (251 females and 332 males; a sex ratio of 1:1.32 respectively). 2) Of the 583 patients with OC, 19% had CL, 39% had CP and 42% had CLP. We found a high occurrence rate of CP among all clefts (CL: CLP: CP – 1:2:2). The most common OC in boys was left-side CLP; in girls it was CP. The left side of the face was damaged 2.2 times more frequently than the right side. 3) Over a third of mothers of children with OC had experienced psychological stress during pregnancy, 45% of mothers had previously undergone at least one medical abortion, and 20% of mothers had been exposed to teratogenic toxic substances. The average birthweight of the children with OC was similar to the birthweight of children without clefts. An association between maternal age and the occurrence of OC could not be observed. 4) The results of this study suggest that several genes known to be involved in craniofacial morphogenesis and/or palatogenesis, may contribute to the incidence of OC. 4.1. Our data provide additional confirmation for the role of MSX1 and MTHFR in the etiology of nonsyndromic CL/P in the Estonian sample. 4.2 We found new supportive evidence that the orofacial clefting locus, OFC3 on Chr 19q13, is probably involved in nonsyndromic CL/P across different populations. 4.3. This study provides, for the first time, evidence of the implication of IRF6, COL2A1, COL11A2 and WNT3 in the occurrence of nonsyndromic CP in north-eastern European populations (Estonians, Latvians, Lithuanians). 4.4. We could not demonstrate convincing evidence of an association between CL/P and IRF6, the candidate gene most consistently replicated. This result could be explained by the various confounding factors and heterogeneity among the populations. 4.5. The present study is the first to demonstrate an association between CL/P and common SNPs and haplotypes in FGF1, and provides new evidence that variation in the TIMP2 and WNT9B genes contributes to nonsyndromic CL/P. 4.6. We have successfully replicated previous findings implicating FOXE1 as a susceptibility locus for CL/P across different populations. 4.7 The results of this study underline the importance of the FGF and Wnt signalling pathway genes in the etiology of both CL/P and CP.
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Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
huulelõhe, suulaelõhe, kaasasündinud haigused, geneetilised aspektid, etioloogia, cleft clip, cleft palate, congenital diseases, genetic aspects, etiology