Opportunities for Detection and Use of QTL Influencing Seasonal Reproduction

1. Opportunities for Detection and Use of QTL Influencing Seasonal Reproduction D. R. Notter1 and N. E. Cockett2 1Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 2Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT

2. ESTABLISHMENT OF A POPULATION FOR SELECTION • Developed from crosses among 3 breeds • 50% Dorset • 25% Rambouillet • 25% Finnsheep • Establishment began in 1983 • Selection began in 1988 • Phase I analyses in 1993 • End selection after fall, 1998 lambing

3. SPRING LAMBING AUTUMN LAMBING Selection Line Genetic Control Line Environmental Control Line Design of Virginia Tech Selection Line

4. Genetic Parameters

5. Fertility (%) in Select and Environmental Control Lines

6. Phase II PerformanceEwe Fertility: 1995-97

7. 16 14 12 10 8 Fertility EBV, % Select 6 4 EC 2 GC 0 -2 1992 1994 1988 1990 1996 Response to Selection

8. Selection line ewe and lambs

9. Duration of Anestrus in High & Low Breeding Value Ewes • Screen high and low BV ewes in 1992, 1993, and 1995 • Place with vasectomized marker rams in mid-Jan.; remove rams around Aug. 1 • Check for matings twice per week • Assay circulating progesterone to confirm ovulation • Calculate duration of anestrus

10. Duration of Anestrus in High & Low Breeding Value Ewes

11. J F M A M J J A L H 1992

12. J F M A M J J A L H 1995

13. Duration of Anestrus in High & Low Breeding Value Ewes • Regression of no. of days anestrus on EBV for fall fertility = -2.15 d/% (P < .01) • Range in EBV for fall fertility in the base population = 30% • Predicted range in no. of days anestrus = 64.5 d

14. J F M A M J J A 97 L H HP 1997

15. Circulating Melatonin & Prolactin • Cooperative with INRA. Evidence in France for strong genetic control of circulating melatonin • Evaluate 182 fall-lambing select and control ewes in August, 1997 • Four nocturnal blood samples at approximately hourly intervals • Levels of each hormone were repeatable (r = .57) between sampling times • No association between circulating melatonin and prolactin

16. Circulating Melatonin and Prolactin Levels • Regressions of Circulating Mel and Prl on EBV for Fall Fertility: • -2.23  .79 ng/ml melatonin per % EBV • 1.16  .40 ng/ml prolactin per % EBV

17. Effect of Continuous Long Days on Estrous Behavior and Circulating Prolactin in Sheep Selected for Spring Fertility J. M. Smith, D. R. Notter, and R. M. Akers Department of Animal and Poultry Sciences Virginia Tech

18. L o n g D a y s N o r m a l D a y s ~12’ Design of Light-Controlled Facility Sliding Door Open Door Alleyway

19. Number of days anestrus for ewes of different ages in normal or long days

20. Circulating progesterone levels for ewes in normal (ND) or long days (LD)

21. Progesterone levels at 20 day intervals following the summer solstice -- N = 10 with continuous long days

22. Genetic Analysis of the Melatonin Receptor Gene • Gene maps to sheep chromosome 26 • Two polymorphic RFLP sites detected in collaboration with Iowa State University • Established a DNA library at Utah State University in 1997

23. Frequencies of Melatonin Receptor Haplotypes p1 = .39; p2 = .33 N = 377

24. All matings Adult matings

25. All matings Adult matings (P = 0.03)

26. Effects of MTNR1A PolymorphismMlnI (Pelletier et al., 2000) • High vs low fertility Merino d’Arles ewes • Frequency of - - less for H than L (0 vs 28.5%) • Found 10 mutations in ≥4 haplotypes with 2 a.a. substitutions • - allele was always associated with Ile → Val

27. Allelic frequencies for the MlnI and RsaI polymorphisms in various breeds

28. Allelic frequencies for MlnI and RsaI polymorphisms from the literature

29. Clock Genes • Circadian rhythms provide the basis for seasonal cycles • Understanding of genes controlling circadian rhythms is expanding rapidly • Complex epistatic interactions are involved, providing opportunities for loss-of-function mutations that modify circadian rhythms • Extension to molecular control of circannual rhythms is just beginning

30. The Clockworks • The central clock appears to be located in the suprachiasmatic nucleus (SCN) • It is autonomous but can be reset, and therefore synchronized, by external cues (light) • To date, 9 major mammalian clock genes have been identified in mouse, hamster, and sheep

31. Clock Bmal1 Timeless Casein kinase 1ε Period1 Period2 Period3 Cryptochrome1 Cryptochrome2 Mammalian Clock Genes

32. “τ” The free-running circadian periodicity in constant light or darkness • Usually determined in rodents by monitoring wheel-running behavior • Normally 23-24 hr with very little variation • Likely very difficult to measure in sheep because of external social cues (and finding a big enough wheel).

33. Clock MutantsThe tau hamster • A mutation within the casein kinase 1ε gene • tau/+ has the circadian periodicity (τ) reduced by ~2 hr, to 22 hr • tau/tau has τ reduced by ~4 hr, to 20 hr • In tau/tau males, no 24-hr light-dark cycle will produce testicular regression • tau/tau animals have more phenotypic variation in τ than +/+ hamsters, so this may be a permissive mutation

34. Expression of Clock Genes in Sheep Brain (Lincoln et al., 2002, 2003) • In SCN, expression of per is induced by light • Without light cues, accumulation of clock —bmal1 heterodimers can also induce per • Expression of clock is relatively independent of light • Formation of per—cry complexes is required for translocation into the nucleus where they supress clock—bmal1 mediated transcription of per

35. ψ ψ PER CRY CRY PER 0 24 ZT (h) 0 24 ZT (h) Expression of per and cry Genes in the PT of Sheep Exposed to Different Photoperiods from Lincoln et al., 2003

36. Gene Interactions in Circadian Cycles • Patterns of expression of per and cry in PT differ from those in SCN of both rodents and sheep • Timing of formation of complexes of per and cry gene products in PT therefore depends of photoperiod

37. ψ ψ PER CRY CRY PER 0 24 ZT (h) 0 24 ZT (h) Expression of per and cry Genes in the PT of Sheep Exposed to Different Photoperiods from Lincoln et al., 2003

38. Calendar Cells (and Genes?) in Sheep • G. Lincoln discussed “calendar” cells in sheep (Lincoln et al., 2003) • Based largely on circannual and other light-mediated changes in circulating prolactin • Suggests the pars tuberalis as the site of calendar cells involved in reproductive transitions • Mutations in clock genes or unknown calendar genes may cause loss in circadian/circannual rhymicity, or permit expression of underlying variation in rhymicity

39. Any Questions?