Sexual development of a model marsupial male

2006 ◽  
Vol 54 (3) ◽  
pp. 151 ◽  
Author(s):  
Marilyn B. Renfree ◽  
Andrew J. Pask ◽  
Geoff Shaw
Keyword(s):  
Sexual Development ◽  
Sexual Differentiation ◽  
Extended Period ◽  
Tammar Wallaby ◽  
Experimental Manipulation ◽  
Exact Role ◽  
Oestrogen Treatment ◽  
Linked Gene ◽  
Macropus Eugenii ◽  
And Control

In eutherian mammals sexual differentiation occurs during fetal development, making experimental manipulation difficult, unlike in marsupials. We are investigating the roles of several key genes and hormones whose exact role in gonadal differentiation is still unclear using the tammar wallaby (Macropus eugenii) as a model. As in humans, unlike in mice, the testis-determining gene SRY is expressed in male tammar fetuses in many tissues over an extended period. Not all sexual differentiation depends on testicular hormones. Scrotum and mammary glands are under the control of X-linked gene(s). Our demonstration of DMRT1 expression in tammar and mouse ovaries suggests it has a wider role than previously thought. The Y-borne copy of ATRX (ATRY) is coexpressed with DMRT1 in developing testis. Gonadal sex reversal can be induced in males by neonatal oestrogen treatment and in females by grafting developing ovaries to males or culturing them in minimal medium. Treatments of developing young with various androgens, and studies of steroid metabolism have shown that the steroid androstenediol may have a previously unrecognised role in virilisation. Our studies using a marsupial model have given some surprising insights into the evolution and control of sexual development in all mammals.

Effects of bromocriptine at parturition in the tammar wallaby, Macropus eugenii

1990 ◽  
Vol 2 (1) ◽  
pp. 79 ◽  
Author(s):  
TP Fletcher ◽  
G Shaw ◽  
MB Renfree
Keyword(s):  
Post Partum ◽  
Tammar Wallaby ◽  
Plasma Prolactin ◽  
Plasma Progesterone ◽  
Macropus Eugenii ◽  
Sequence Of Events ◽  
Prostaglandin Release ◽  
Peripartum Period ◽  
And Control ◽  
Subsequent Onset

Female tammar wallabies were treated with the dopamine agonist bromocriptine at the end of pregnancy to suppress the peripartum pulse of plasma prolactin. The animals were subsequently observed, and a series of blood samples taken to define the hormonal profiles before and immediately after parturition. Birth was observed in 4/5 control animals and occurred in 8/9 bromocriptine-treated animals. The peripartum peak in plasma PGFM concentrations was not affected by bromocriptine although the pulse of prolactin normally seen at parturition was completely abolished. The timing of luteolysis was apparently unaffected, as plasma progesterone concentrations fell similarly in both treated and control animals immediately after parturition. However, all of the neonates of the bromocriptine-treated animals died within 24 h, possibly because of a failure to establish lactation. Subsequent onset of post-partum oestrus was delayed or absent both in control and in bromocriptine-treated animals, suggesting that the frequent blood sampling and disturbances in the peripartum period interfered with these endocrine processes. It is concluded that both prolactin and prostaglandin can induce luteolysis in the pregnant wallaby, but that the normal sequence of events results from a signal of fetal origin inducing a prostaglandin release from the uterus, which in turn releases a pulse of prolactin that induces a progesterone decline.

scholarly journals Parturition and perfect prematurity: birth in marsupials

2006 ◽  
Vol 54 (3) ◽  
pp. 139 ◽  
Author(s):  
Geoff Shaw ◽  
Marilyn B. Renfree
Keyword(s):  
Reproductive Tract ◽  
Tammar Wallaby ◽  
Experimental Manipulation ◽  
Lung Maturation ◽  
Plasma Progesterone ◽  
Macropus Eugenii ◽  
Surfactant Production ◽  
Glucocorticoid Production ◽  
The Brain ◽  
Adrenal Glucocorticoid

Marsupials are distinguished from eutherian mammals in their mode of reproduction. They give birth to a highly altricial young, which completes its development whilst attached to a teat, usually within a pouch. The marsupial neonate has relatively well-developed digestive, respiratory and circulatory systems but retains its fetal excretory system with a fully functional mesonephric kidney and undifferentiated gonads and genitalia. We have investigated birth in the tammar wallaby (Macropus eugenii) and shown that the tiny (400 mg) fetus determines the time of its own delivery. Although plasma progesterone falls, and oestradiol associated with the postpartum oestrus typically rises, around the time of parturition, neither hormone is essential for the timing of birth. However relaxin may loosen the connective tissue of the cervix and vaginae for birth. Labour starts suddenly and is completed within minutes. Both prostaglandins and mesotocin are essential for the contractions that deliver the young. Prostaglandins from the reproductive tract act via the brain to control parturient behaviour. In the last 2 days of gestation fetal adrenal glucocorticoid production increases, promoting lung maturation and surfactant production and ultimately triggering labour. The accessibility of the altricial neonatal marsupial provides a unique opportunity for experimental manipulation of organ development and maturation.

scholarly journals Growth of the corpus luteum and its progesterone content during pregnancy in the tammar wallaby, Macropus eugenii

Reproduction ◽  
1979 ◽  
Vol 57 (1) ◽  
pp. 131-136 ◽  
Author(s):  
M. B. Renfree ◽  
S. W. Green ◽  
I. R. Young
Keyword(s):  
Corpus Luteum ◽  
Tammar Wallaby ◽  
Macropus Eugenii

Mullerian inhibiting substance production and testicular migration and descent in the pouch young of a marsupial

Development ◽  
1988 ◽  
Vol 104 (4) ◽  
pp. 549-556 ◽  
Author(s):  
J.M. Hutson ◽  
G. Shaw ◽  
W.S. O ◽  
R.V. Short ◽  
M.B. Renfree
Keyword(s):  
Tammar Wallaby ◽  
Testicular Descent ◽  
Future Studies ◽  
Macropus Eugenii ◽  
Müllerian Inhibiting Substance ◽  
Sequence Of Events ◽  
Testicular Differentiation ◽  
Testicular Migration ◽  
Australian Marsupial ◽  
Mullerian Inhibiting Substance

The ontogeny of Mullerian inhibiting substance (MIS) production by the developing testis of an Australian marsupial, the tammar wallaby (Macropus eugenii), was determined during pouch life using an organ-culture bioassay of mouse fetal urogenital ridge. This information was related to the morphological events during testicular migration and descent. MIS biological activity was found in testes (but not ovaries or liver) of pouch young from 2 to 85 days of age. MIS production had commenced by day 2, which is within a day of the first gross morphological signs of testicular differentiation. Mullerian duct regression occurred between 10 and 30 days, which partly coincided with testicular migration to the inguinal region and enlargement of the gubernacular bulb (15 to 30 days). These observations are consistent with the hypothesis that MIS may be involved in testicular transabdominal migration. The epididymis commenced development and growth only after the testis had descended through the inguinal ring. This provides no support for the suggestion that the epididymis is involved in testicular descent into the scrotum. The basic sequence of events in post-testicular sexual differentiation in the wallaby is sufficiently similar to that seen in eutherian mammals to make it an excellent experimental model for future studies of testicular differentiation, migration and descent.

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