Modepalli Vengamanaidu, Kumar Amit, Hinds Lyn A, Sharp Julie A, Nicholas Kevin R, Lefevre Christophe
School of medicine, Deakin University, Pigdons Road, Geelong, Vic, Australia.
BMC Genomics. 2014 Nov 23;15(1):1012. doi: 10.1186/1471-2164-15-1012.
Lactation is a key aspect of mammalian evolution for adaptation of various reproductive strategies along different mammalian lineages. Marsupials, such as tammar wallaby, adopted a short gestation and a relatively long lactation cycle, the newborn is immature at birth and significant development occurs postnatally during lactation. Continuous changes of tammar milk composition may contribute to development and immune protection of pouch young. Here, in order to address the putative contribution of newly identified secretory milk miRNA in these processes, high throughput sequencing of miRNAs collected from tammar milk at different time points of lactation was conducted. A comparative analysis was performed to find distribution of miRNA in milk and blood serum of lactating wallaby.
Results showed that high levels of miRNA secreted in milk and allowed the identification of differentially expressed milk miRNAs during the lactation cycle as putative markers of mammary gland activity and functional candidate signals to assist growth and timed development of the young. Comparative analysis of miRNA distribution in milk and blood serum suggests that milk miRNAs are primarily expressed from mammary gland rather than transferred from maternal circulating blood, likely through a new putative exosomal secretory pathway. In contrast, highly expressed milk miRNAs could be detected at significantly higher levels in neonate blood serum in comparison to adult blood, suggesting milk miRNAs may be absorbed through the gut of the young.
The function of miRNA in mammary gland development and secretory activity has been proposed, but results from the current study also support a differential role of milk miRNA in regulation of development in the pouch young, revealing a new potential molecular communication between mother and young during mammalian lactation.
哺乳是哺乳动物进化的一个关键方面，有助于不同哺乳动物谱系适应各种繁殖策略。有袋类动物，如短尾矮袋鼠，妊娠期短而哺乳期相对较长，新生儿出生时不成熟，在哺乳期会发生显著的产后发育。短尾矮袋鼠乳汁成分的持续变化可能有助于育儿袋幼崽的发育和免疫保护。在此，为了探究新发现的分泌性乳汁微小RNA（miRNA）在这些过程中的假定作用，对哺乳期不同时间点收集的短尾矮袋鼠乳汁中的miRNA进行了高通量测序。并进行了比较分析，以确定miRNA在哺乳期袋鼠乳汁和血清中的分布情况。
结果表明，乳汁中分泌的miRNA水平较高，并且能够识别出哺乳期不同阶段差异表达的乳汁miRNA，它们被假定为乳腺活动的标志物以及辅助幼崽生长和定时发育的功能性候选信号。乳汁和血清中miRNA分布的比较分析表明，乳汁中的miRNA主要在乳腺中表达，而非从母体循环血液中转移而来，可能是通过一种新的假定外泌体分泌途径。相比之下，与成年动物血液相比，在新生动物血清中能够检测到高表达的乳汁miRNA，且水平显著更高，这表明乳汁miRNA可能通过幼崽的肠道被吸收。
虽然已经提出了miRNA在乳腺发育和分泌活动中的功能，但本研究结果也支持乳汁miRNA在调节育儿袋幼崽发育中具有不同作用，揭示了哺乳动物哺乳期母婴之间一种新的潜在分子通讯方式。
