dc.description.abstract |
LncRNAs have emerged as sentinels in the regulation of various cellular processes
and hence, it is not surprising that the number of long non-coding RNA genes
correlate with developmental complexity over the course of evolution. The
versatility of RNA as a biomolecule has been instrumental in its participation in
diverse cellular contexts.
Meiotic recombination hotspot locus (Mrhl) is a long non-coding RNA that was
discovered in our laboratory. It showed a tissue specific expression pattern and was
highly expressed in testis, liver, spleen and kidneys (38). Owing to its high
expression in adult testis, the initial characterization of the RNA was carried out in
a B-type mouse spermatogonial cell line GC1-spg. In these cells, Mrhl was seen to
be a nuclear restricted RNA that was processed to a 80 nucleotide transcript by
Drosha machinery (39). Further, it was shown to be a chromatin associated RNA
with a role in regulating gene expression of several loci (some of which were
exerted by its physical association) (42). Functional analysis of the RNA revealed its
role in the regulation of one of the important signaling pathway, Wnt, which is
crucial all along the course of development. Wnt signaling in turn negatively
regulates Mrhl, forming a feedback loop (40). This interplay between Mrhl and Wnt
has been extensively characterized in our laboratory and has been found to be a key
step in meiotic commitment of mouse spermatogonial cells (41).
Since long non-coding RNAs exhibit tissue specific and context specific function,
the present study involves the basic characterization of Mrhl in mouse embryonic
stem cells. We find that similar to mouse spermatogonial cells, Mrhl is a nuclear
restricted and chromatin associated RNA. However, unlike the case in Gc1-spg
cells, Mrhl does not interact with p68, a DEAD box helicase. This interaction of
Mrhl with p68 is instrumental in its regulation of Wnt- signaling. Hence, it was not
surprising to find that in mouse embryonic stem cells, down regulation of Mrhl
does not result in the nuclear translocation of beta- catenin, which is a hallmark of
canonical Wnt signaling activation (unpublished work; Iyer, D.).To understand the function exerted by Mrhl in mouse embryonic stem cells, we
resorted to two approaches. Firstly, upon down regulation of the RNA, we find no
change in the pluripotency markers indicating that Mrhl is not directly involved in
the maintenance of pluripotency. Further insights into the functions of the RNA
will be obtained by global gene expression profiling upon down regulation of Mrhl.
Additionally, preliminary results suggest that Mrhl is up regulated as mouse
embryonic stem cells undergo differentiation. The second approach employed was
to determine the interacting protein partners of the Mrhl by RNA pull-down
followed by mass spectrometric analysis.
It will be interesting to know the repertoire of interacting partners the RNA can
have and the list of processes it might be regulating in this context. Since Mrhl is
chromatin bound in mouse embryonic stem cells too, it will be enlightening to map
the genome wide occupancy of this RNA in this system, which is epigenetically
quite unique. Also, these studies will also provide us with a comparative analysis of
the common and exclusive roles Mrhl can carry out in these two different systems. |
en_US |