Title Polimorfizmi gena uključenih u metabolizam folata kao rizični čimbenici trisomije 21 : doktorski rad
Title (english) Polymorphisms of genes involved in folate metabolism as risk factors for trisomy 21
Author Jadranka Vraneković MBZ: 270140
Mentor Bojana Brajenović-Milić (mentor)
Committee member Blaženka Grahovac (predsjednik povjerenstva)
Committee member Borut Peterlin https://orcid.org/0000-0001-7824-4978 (član povjerenstva)
Committee member Oleg Petrović (član povjerenstva)
Committee member Bojana Brajenović-Milić (član povjerenstva)
Granter University of Rijeka Faculty of Medicine Rijeka
Defense date and country 2012-05-10, Croatia
Scientific / art field, discipline and subdiscipline BIOMEDICINE AND HEALTHCARE Clinical Medical Sciences Clinical Biochemistry
Universal decimal classification (UDC ) 616 - Pathology. Clinical medicine
Abstract Cilj ovog istraživanja bio je utvrditi predstavljaju li polimorfizmi gena
MTHFR C677T/A1298C i MTRR A66G, pojedinačno ili u kombinaciji, rizične
čimbenike za nerazdvajanje kromosoma 21 u majki djece s DS-om i to s obzirom
na starosnu dob, mejotičku diobu te broj i položaj rekombinacije.
Ispitanici i metode: U istraživanju je sudjelovalo 116 obitelji od kojih je 76 bilo
tročlanih (majka, otac i dijete s DS) i 40 dvočlanih (majka i dijete s DS). U svim
slučajevima DS-a (N=116) radilo se o regularnom tipu trisomije 21. Kontrolnu
grupu majki (N=141) i očeva (N=101) činile su osobe koje su imale zdravu djecu i
urednu obiteljsku i osobnu anamnezu. Ispitanici i kontrole usklađeni su po dobi. Za
određivanje roditeljskog podrijetla trisomije 21, mejotičke diobe te broja i položaja
rekombinacije koristila se PCR-STR metoda. Genotipizacija polimorfizama
MTHFR C677T/A1298C i MTRR A66G je izvedena PCR-RFLP metodom. Za
usporedbu učestalosti alela i genotipova koristio se
test i Fisherov egzaktni test.
Procjena rizika alela, genotipova i njihovih kombinacija za trisomiju 21 temeljila se
na omjeru izgleda i pripadajućeg 95% raspona pouzdanosti. Povezanost
pojedinačnih polimorfizama s nerazdvajanjem kromosoma u MI i MII diobi te
brojem i položajem rekombinacija testirala se Spearmanovim rank korelacijskim
testom. Statistička značajnost određivana je na razini p 0,05.
Rezultati: Od ukupno 116 obitelji u 102 (88%) je uspješno određeno podrijetlo DSa. Majčino podrijetlo trisomija 21 utvrđeno je u 93% slučajeva i znatno su češće
nastale kao posljedica nerazdvajanja kromosoma u MI (86%) nego u MII diobi
(14%). Očevo podrijetlo utvrđeno je u 5%, a postzigotno u 2% slučajeva DS-a.
Majke djece s trisomijom 21 majčinog podrijetla starije su od majki djece s DS-om
očevog i/ili postzigotnog podrijetla (P=0,010). U trisomija 21 majčinog podrijetla
nastalih nerazdvajanjem kromosoma u MI diobi izostanak rekombinacije utvrđen je
u 79%, jedna rekombinacija u 18%, a dvije rekombinacije u 3% slučajeva. U
slučajevima s utvrđenom samo jednom rekombinacijom ona je najčešće
smještena u distalnom dijelu kromosoma (60%). U trisomija 21 nastalih
nerazdvajanjem kromosoma u MII diobi utvrđen je pericentromerni položaj
rekombinacije u svim slučajevima s jednom rekombinacijom. Učestalost broja i
položaja rekombinacija u MI i MII diobi nije se statistički značajno razlikovala
ovisno o dobnoj skupini majki djece s DS-om. Učestalost alela i genotipova
MTHFR C677T/A1298C i MTRR A66G polimorfizama, pojedinačno ili u
kombinaciji, nije se statistički značajno razlikovala između ispitivanih skupina majki.
Razlike nisu utvrđene ni obzirom na starosnu dob majke, mejotičku diobu, broj i
položaj rekombinacija. U očeva djece s DS-om utvrđena je statistički značajno
manja učestalost MTHFR 1298CC genotipa u odnosu na grupu kontrolnih očeva
(P = 0,029). Učestalost ostalih genotipova i alela MTHFR C677T/A1298C i MTRR
A66G polimorfizama nije se statistički značajno razlikovala između očeva djece s
DS-om i kontrolne grupe.
Zaključak: Rezultati našeg istraživanja pokazali su da MTHFR C677T/A1298C i
MTRR A66G polimorfizmi, pojedinačno ili u kombinaciji, ne predstavljaju rizične
čimbenike majke za trisomiju 21 majčinog podrijetla. Istovremeno, promijenjen
obrazac rekombinacije potvrđen je kao rizični čimbenik nepravilnog razdvajanja
kromosoma tijekom mejoze, ali nije dokazana povezanost s prisustvom ispitivanih
polimorfizama.
Abstract (english) Aim: This study aimed to determine whether polymorphisms of MTHFR
C677T/A1298C and MTRR A66G genes, individually or in combination,
represented risk factors for the nondisjunction of chromosome 21 in mothers of
children with Down Syndrome (DS), considering age, meiotic division, and the
numbers and locations of recombinations.
Patients and methods: The study included 116 families; 76 were three-member
families (mother, father, and child with DS), and 40 were two-member families
(mother and child with DS). All DS cases (N = 116) exhibited full trisomy 21. A
control group of mothers (N = 141) and fathers (N = 101) consisted of individuals
that had a healthy child and no personal or family history of trisomy 21. Subjects
and controls were age-matched. PCR genotyping with short tandem repeats was
used to determine the parental origin of trisomy 21, meiotic division stage, and the
numbers and locations of recombinations. PCR with restriction fragment length
polymorphisms was performed to detect MTHFR C677T/A1298C and MTRR
A66G polymorphisms. The frequencies of alleles and genotypes were compared
between groups with the
2
and Fisher's exact tests. Odds ratios and 95%
confidence intervals were calculated to evaluate the allele/genotype risk for
trisomy 21. The Spearman rank correlation test was used to test whether
individual polymorphisms were associated with chromosome nondisjunctions in
meiotic MI and MII divisions or with the numbers and locations of recombinations.
Statistical significance was set at P < 0.05.
Results: The parental origin of DS was successfully determined in 102 (80%) out
of 116 families. Maternal origin of trisomy 21 was found in 93% of cases and was
caused by chromosome nondisjunction in the MI (86%) more often than in the MII
(14%) division. Paternal origin was found in 5% of cases; mitotic origin occurred in
2% of cases. Mothers of children with trisomy 21 of maternal origin were older
than mothers of children with DS of paternal and/or mitotic origin (P = 0.010). In
trisomy 21 of maternal origin that resulted from chromosome nondisjunction in the
MI division, no recombinations occurred in 79%, one recombination occurred in 18%, and two recombinations occurred in 3% of cases. In cases with a single
recombination event, recombination was most commonly located in the distal part
of the chromosome (60%). In trisomy 21 caused by chromosome nondisjunction in
the MII division, a pericentromeric recombination location was established in all
cases with a single recombination event. The frequency distributions of the
numbers and locations of recombinations in MI and MII divisions were not
significantly different among the different maternal age groups (young ≤36; older
36). No significant differences were found between case and control groups in
the frequency of alleles, genotypes, or genotype combinations of the MTHFR
C677T/A1298C and MTRR A66G polymorphisms. Additionally, no significant
differences were found in the frequency of alleles, genotypes, or genotype
combination in case group of mothers according to maternal age, meiotic division,
or the numbers and locations of recombinations. Fathers of children with DS
showed significantly lower frequencies of the MTHFR 1298CC genotype
compared to the control group of fathers (P = 0.029). The frequency distribution of
other genotypes and alleles with MTHFR C677T/A1298C and MTRR A66G
polymorphisms was not statistically significantly different between the fathers of
children with DS and the control group of fathers.
Conclusion: Our findings showed that the MTHFR C677T/A1298C and MTRR
A66G polymorphisms, individually or in combination, did not represent risk factors
for maternal trisomy 21. Although we confirmed that altered recombination was a
risk factor for improper separation of chromosomes during meiosis, we did not find
an association with the presence of the investigated polymorphisms.
Keywords
Down sindrom
Genetička rekombinacija
Genski polimorfizam
Kromosomsko nerazdvajanje
Metilentetrahidrofolat-reduktaza
Metiltetrahidrofolat-homocistein metiltransferaza reduktaza
Trisomija 21
Keywords (english)
Down Syndrome
Methylenetetrahydrofolate reductase
Methyltetrahydrofolate-homocysteine methyltransferase reductase
Nondisjunction
Genetic
Polymorphism
Genetic
Recombination
Genetic
Trisomy 21
Language croatian
URN:NBN urn:nbn:hr:188:402444
Promotion 2012-05-10
Study programme Title: Biomedicine Postgraduate (doctoral) study programme Study programme type: university Study level: postgraduate Academic / professional title: doktor/doktorica znanosti, područje biomedicine i zdravstvo (doktor/doktorica znanosti, područje biomedicine i zdravstvo)
Catalog URL https://libraries.uniri.hr/cgi-bin/unilib.cgi?form=D1121219060
Type of resource Text
Extent 115 str; 30 cm
File origin Born digital
Access conditions Open access
Terms of use
Created on 2017-01-19 17:16:31