We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhi... more We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation.
Genomic imprinting is a widespread epigenetic phenomenon in eutherian mammals that regulates many... more Genomic imprinting is a widespread epigenetic phenomenon in eutherian mammals that regulates many aspects of growth and development. Parental conflict over the degree of maternal nutrient transfer is the favoured hypothesis for the evolution of imprinting. Marsupials, like eutherian mammals, are viviparous but deliver an altricial young after a short gestation supported by a fully functional placenta, so can shed light on the evolution and time of acquisition of genomic imprinting. All orthologues of eutherian imprinted genes examined have a conserved expression in the marsupial placenta regardless of their imprint status. Differentially methylated regions are the most common mechanism controlling genomic imprinting in eutherian mammals, but none were found in the marsupial imprinted orthologues of insulin-like growth factor 2 receptor (IGF2R), INS or mesoderm specific transcript (MEST).
Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals h... more Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals have a yolk sac, but while both chorio-allantoic and chorio-vitelline (yolk sac) placentation can occur, most marsupials only develop a yolk sac placenta. Insulin (INS) is unusual in that it is the only gene that is imprinted exclusively in the yolk sac placenta. Marsupials, therefore, provide a unique opportunity to examine the conservation of INS imprinting in mammalian yolk sac placentation. Marsupial INS was cloned and its imprint status in the yolk sac placenta of the tammar wallaby, Macropus eugenii, examined. In two informative individuals of the eight that showed imprinting, INS was paternally expressed. INS protein was restricted to the yolk sac endoderm, while insulin receptor, IR, protein was additionally expressed in the trophoblast. INS protein increased during late gestation up to 2 days before birth, but was low the day before and on the day of birth. The conservation of im...
ABSTRACT At birth all mammalian neonates depend on finding the milk source in order to survive. T... more ABSTRACT At birth all mammalian neonates depend on finding the milk source in order to survive. The development of mammalian young ranges from precocial to highly altricial, but olfaction plays an essential role in the milk-finding process in all mammalian species studied, along with other sets of cues depending on the development of the neonate 's sensory systems. Of all mammals studied, so far marsupials and monotreme are the least developed at birth and have the least developed olfactory systems. Nonetheless the neonates are able to reach the pouch ancl the teat or milk patches unaided by their mothers. Behavioural studies confirm that olfaction pays a role in guiding the young to the pouch and teat and may be responsible for the switch in direction at the lip of the pouch in the tammar wallaby to climb down into the pouch and attach to a teat. The switch in direction at the pouch entrance may be triggered by olfactory cues acting via this the main olfactory system, as it is further developed than the accessory olfactory system. However, the latter may serve as a backup if the main olfactory system fails . How the information is processed by the poorly developed neonatal brain to control the movements and behaviour of marsupial and monotreme young remains to be investigated. http://link.springer.com/chapter/10.1007%2F978-1-4614-5927-9_7
Maturation of the mammalian growth axis is thought to be linked to the transition from fetal to p... more Maturation of the mammalian growth axis is thought to be linked to the transition from fetal to post-natal life at birth. However, in an altricial marsupial, the tammar wallaby (Macropus eugenii), this process occurs many months after birth but at a time when the young is at a similar developmental stage to that of neonatal eutherian mammals. Here we manipulate growth rates and demonstrate in slow, normal and fast growing tammar young that nutrition and growth rate affect the time of maturation of the growth axis. Maturation of GH/IGF-I axis components occurred earlier in fast growing young, which had significantly increased hepatic GHR, IGF1 and IGFALS expression, plasma IGF-I concentrations, and significantly decreased plasma GH concentrations compared to age-matched normal young. These data support the hypothesis that the time of maturation of the growth axis depends on the growth rate and maturity of the young, which can be accelerated by changing their nutritional status.
The International journal of developmental biology, 2014
The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal. Reproduc... more The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal. Reproduction in the tammar is seasonal, regulated by photoperiod and also lactation. Reactivation is triggered by falling daylength after the austral summer solstice in December. Young are born late January and commence a 9-10-month lactation. Females mate immediately after birth. The resulting conceptus develops over 6- 7 days to form a unilaminar blastocyst of 80-100 cells and enters lactationally, and later seasonally, controlled diapause. The proximate endocrine signal for reactivation is an increase in progesterone which alters uterine secretions. Since the diapausing blastocyst is surrounded by the zona and 2 other acellular coats, the mucoid layer and shell coat, the uterine signals that maintain or terminate diapause must involve soluble factors in the secretions rather than any direct cellular interaction between uterus and embryo. Our studies suggest involvement of a number of cytokine...
We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhi... more We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation.
Genomic imprinting is a widespread epigenetic phenomenon in eutherian mammals that regulates many... more Genomic imprinting is a widespread epigenetic phenomenon in eutherian mammals that regulates many aspects of growth and development. Parental conflict over the degree of maternal nutrient transfer is the favoured hypothesis for the evolution of imprinting. Marsupials, like eutherian mammals, are viviparous but deliver an altricial young after a short gestation supported by a fully functional placenta, so can shed light on the evolution and time of acquisition of genomic imprinting. All orthologues of eutherian imprinted genes examined have a conserved expression in the marsupial placenta regardless of their imprint status. Differentially methylated regions are the most common mechanism controlling genomic imprinting in eutherian mammals, but none were found in the marsupial imprinted orthologues of insulin-like growth factor 2 receptor (IGF2R), INS or mesoderm specific transcript (MEST).
Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals h... more Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals have a yolk sac, but while both chorio-allantoic and chorio-vitelline (yolk sac) placentation can occur, most marsupials only develop a yolk sac placenta. Insulin (INS) is unusual in that it is the only gene that is imprinted exclusively in the yolk sac placenta. Marsupials, therefore, provide a unique opportunity to examine the conservation of INS imprinting in mammalian yolk sac placentation. Marsupial INS was cloned and its imprint status in the yolk sac placenta of the tammar wallaby, Macropus eugenii, examined. In two informative individuals of the eight that showed imprinting, INS was paternally expressed. INS protein was restricted to the yolk sac endoderm, while insulin receptor, IR, protein was additionally expressed in the trophoblast. INS protein increased during late gestation up to 2 days before birth, but was low the day before and on the day of birth. The conservation of im...
ABSTRACT At birth all mammalian neonates depend on finding the milk source in order to survive. T... more ABSTRACT At birth all mammalian neonates depend on finding the milk source in order to survive. The development of mammalian young ranges from precocial to highly altricial, but olfaction plays an essential role in the milk-finding process in all mammalian species studied, along with other sets of cues depending on the development of the neonate 's sensory systems. Of all mammals studied, so far marsupials and monotreme are the least developed at birth and have the least developed olfactory systems. Nonetheless the neonates are able to reach the pouch ancl the teat or milk patches unaided by their mothers. Behavioural studies confirm that olfaction pays a role in guiding the young to the pouch and teat and may be responsible for the switch in direction at the lip of the pouch in the tammar wallaby to climb down into the pouch and attach to a teat. The switch in direction at the pouch entrance may be triggered by olfactory cues acting via this the main olfactory system, as it is further developed than the accessory olfactory system. However, the latter may serve as a backup if the main olfactory system fails . How the information is processed by the poorly developed neonatal brain to control the movements and behaviour of marsupial and monotreme young remains to be investigated. http://link.springer.com/chapter/10.1007%2F978-1-4614-5927-9_7
Maturation of the mammalian growth axis is thought to be linked to the transition from fetal to p... more Maturation of the mammalian growth axis is thought to be linked to the transition from fetal to post-natal life at birth. However, in an altricial marsupial, the tammar wallaby (Macropus eugenii), this process occurs many months after birth but at a time when the young is at a similar developmental stage to that of neonatal eutherian mammals. Here we manipulate growth rates and demonstrate in slow, normal and fast growing tammar young that nutrition and growth rate affect the time of maturation of the growth axis. Maturation of GH/IGF-I axis components occurred earlier in fast growing young, which had significantly increased hepatic GHR, IGF1 and IGFALS expression, plasma IGF-I concentrations, and significantly decreased plasma GH concentrations compared to age-matched normal young. These data support the hypothesis that the time of maturation of the growth axis depends on the growth rate and maturity of the young, which can be accelerated by changing their nutritional status.
The International journal of developmental biology, 2014
The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal. Reproduc... more The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal. Reproduction in the tammar is seasonal, regulated by photoperiod and also lactation. Reactivation is triggered by falling daylength after the austral summer solstice in December. Young are born late January and commence a 9-10-month lactation. Females mate immediately after birth. The resulting conceptus develops over 6- 7 days to form a unilaminar blastocyst of 80-100 cells and enters lactationally, and later seasonally, controlled diapause. The proximate endocrine signal for reactivation is an increase in progesterone which alters uterine secretions. Since the diapausing blastocyst is surrounded by the zona and 2 other acellular coats, the mucoid layer and shell coat, the uterine signals that maintain or terminate diapause must involve soluble factors in the secretions rather than any direct cellular interaction between uterus and embryo. Our studies suggest involvement of a number of cytokine...
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Papers by Geoffrey Shaw