1. Investigating the role of Piwi
Proteins in Hydractinia echinata
Introduction: Piwi genes have been used as stem/germ cell markers in many models such as Drosophila, planarians and mice. Piwi plays
an important role in the maintenance of germ stem cells, fertility, and regeneration. The function of this protein in Hydractinia remains
unclear. I hypothesize that Piwi, along with a role in fertility, plays other roles in stem cells related to gene expression. Through the use of
transgenic animal lines ectopically expressing Piwi and knockdown by RNAi I will gain further insight into the role of this protein.
Emma Mc Mahon1, Christine Schnitzler2, Brian Bradshaw1, Uri Frank1
1 NUI Galway , 2 NHGRI, NIH
Figure 1: Hydractinia body plan showing simple morphology and
the presence of stem cells termed i-cells.
Figure 2: Piwi genes are highly conserved across many species.
Hydractinia have two Piwi homologues termed Piwi1 and Piwi2.
Figure 4: Gene expression pattern of Hydractinia Piwi genes.
From left to right: eggs, larva, female and male gonads of
Piwi1(A) and Piwi2 (B) genes.
A.
B.
A. B. C.
Figure 3: Gene expression pattern in adult feeding polyps of
Piwi1(A) and Piwi2 (B). Immunohistochemisrty staining showing
Piwi1 (C) in adult feeding polyp.
Figure 5: (A) 2 day old larva and (B) same animal under blue light
showing GFP positive cells after injection with GFP mRNA. (C)
mRNA encoding Piwi1::GFP will be injected in the near future.
A. B.
C.
C.
Discussion: The two Piwi genes are expresed in i-cells. It has
been shown that knockdown of Piwi1 inhibits head regeneration
(Bradshaw et al., 2015). I plan to continue with knockdown of
both genes along with ectopic expression studies to find novel
Piwi roles.
Figure 6: Transgenic
Hydractinia colony
expressing GFP under the
endogenous Piwi1 genomic
control elements. Expression
pattern matches that of in
situ mRNA and immuno
staining.Bradshaw et al., 2015