En del av grisens kromosom 4 kan förklara fettansättning
En kvantitativ egenskap är en egenskap som påverkas av flera gener och miljön. Exempel på kvantitativa egenskaper är fettansättning, längd och vikt. Genom att använda Quantitative Trait Locus (QTL) analys kan man koppla en kvantitativ egenskap till en del av en kromosom. För att kunna genomföra denna analys krävs det att man korsar två raser som skiljer sig åt i den egenskap man är intresserad av. Man följer sedan hur egenskapen nedärvs i flera generationer. De domesticerade vita grisarna (Large White) är större, köttigare och har mindre fett än vildsvinet vilket beror på många års selektion för dessa egenskaper. De stora skillnaderna mellan den vita grisen och vildsvinet gör korsningen mellan dessa lämplig för en QTL analys.
Detta arbete är baserat på en korsning mellan den vita grisen och vildsvinet som genomfördes i slutet av 1980-talet. Då identifierades en region på kromosom 4 hos grisen vilken svarar för 20% av skillnaden i fettansättning mellan raserna. Syftet med min forskning har varit att karakterisera denna kromosomregion och att identifiera bakomliggande gener. Med hjälp av olika metoder har vi kunnat minska regionen och våra resultat visar att den innehåller två segment som påverkar bukfett respektive underhudsfett. Vi har hittat en förändring i DNA sekvensen (mutation) som skulle kunna förklara skillnaden i bukfett men fortsatta studier skall göras för att konfirmera detta fynd. Eftersom grisen genetiskt sett är mycket lik oss människor är vår forskning intressant både för köttproduktion och för forskning om fetma hos människor. Fetma är ett växande problem i världen och man har bl.a. sett samband mellan fetma, framförallt bukfett, och typ 2 diabetes.
Grisen saknar brun fettvävnad
Brun fettvävnad finns i stor utsträckning hos nyfödda däggdjur, gnagare och hos djur som går i ide. Denna vävnad hjälper till att bibehålla kroppstemperaturen. Vid fettnedbrytningen i vanlig fettvävnad produceras molekyler som lagrar energi, ATP. I brun fettvävnad frigörs nästan all energi i form av värme. Man har inte identifierat brun fettvävnad hos gris eller påvisat existensen av proteinet uncoupling protein 1 (UCP1) som är specifikt för brun fettvävnad. UCP1-proteinet är nödvändigt för att bilda värme i stället för ATP. Vi har sekvenserat UCP1-genen hos gris och visat att genen inaktiverades (slogs ut) för ca 20 miljoner år sedan. Avsaknaden av
UCP1-proteinet och brun fettvävnad kan förklara varför griskultingar huttrar för att hålla värmen. Vid svinuppfödning används värmelampor för att hålla nyfödda griskultingar varma. Grisen är också det enda klövdjur som bygger bo åt sina ungar.
Acknowledgements
The studies presented in this thesis were carried out at the Department of Animal Breeding and Genetics at the Swedish University of Agricultural Sciences and at the Department of Medical Biochemistry and Microbiology at Uppsala University.
The project was supported by the Foundation for Strategic Research and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.
I would like to express my gratitude to all people that have supported and encouraged me during these years.
I would particularly like to thank:
Leif Andersson, main supervisor, for your guidance during this time. Your
expertise and passion for science is very inspiring! I have learnt very much from you.
Maria Moller, co-supervisor, for introducing me to the lab and for all help
and support during these years. Thank you for being an active supervisor even after moving from Uppsala. I really appreciate that.
Stefan Marklund, co-supervisor, for always taking the time to answer my
questions, for all assistance in the lab and for valuable discussions. See you at “Vasaloppet” next year?!
All co-authors for fruitful collaborations, especially Susanne Stern and
Kjell Andersson for statistical analyses, Susan Ansell for all the BAC’s and Emmanuelle Bourneuf, it has been struggling and stimulating, good luck
with your new position in France.
All former and present members of the lab for a good research atmosphere.
Keep it up!! Thank you for all your encouragement and many laughs. I have really enjoyed the time.
Ulle, my roommate, it has been so much fun sharing the office with you,
thanks for putting up with me -. We have had many talks about science and life. (What do we not know about each other?!..)
Lina and Susanne, for many valuable discussions about science and life,
pep talks and for generously sharing your experiences and knowledge. You have been a tremendous support during these years. Lina, it was a great idée to join the mentor-program, thanks.
Ulla Gustafson, for all sequences and lab support and Gudrun Wieslander,
for help with administrative matters and nice talks. The lab wouldn’t manage without you!
Ulla Schmidt and others at Lövsta for taking care of the pigs and providing
all the blood samples.
All friends and colleagues from the UGSBR year, what a fantastic year! Thanks to the SNiB-2005 committee, it was productive and fun working with you.
Helena Mannerfelt, my mentor, for all support, encouragement and
guidelines for my future career. I always felt full with self-confidence after our meetings.
To ALL my friends outside the “lab world”, for keeping my mind of science and for being fantastic friends. You all mean so much to me!
My dearest family, mum, dad and my sister Karin, thank you for always being there, you are the best family one can wish for.
Oskar, for your love and understanding and for always looking at life from
the bright side. When I am with you I feel happy and confident. You are my love, my friend and everything…
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