The role of Ultrabithorax and its related lncRNAs in the differentiation of lamellocyte in Drosophila

Abstract

Along the anterior-posterior body axis, Hox genes are initial determinants of cell fate across bilaterians. In a number of organogenesis processes in a range of animals, including mammalian, several late non-homeotic regulations of Hox genes have been found. Recent studies have found that the Hox genes are mis-expressed in a variety of cancers, including acute myeloid leukemia. The Hox gene Ultrabithorax (Ubx) encodes a homeodomain transcription factor that regulates morphogenesis in Drosophila melanogaster. Despite its well-defined function in embryogenesis, it is not clear whether Ubx plays a role in hematopoiesis or innate immunity in Drosophila hemocytes. With single-cell RNA sequencing, previous studies have shown that Ubx mRNA is also expressed in Drosophila circulating hemocytes of which transcripts are not found in hemocytes in the lymph gland. In circulating hemocytes, Ubx is not localized in the nucleus where Ubx normally is found, but present in the cytoplasm under normal growing conditions. Interestingly, the nuclear localization of Ubx is enhanced when larvae are challenged by the parasitoid wasp, Leptopilina boulardi. When the Ubx is knocked-out by hemocyte specific CRISPR/Cas9 and Ubx guide RNA expression, the number of lamellocyte in larval blood upon wasp infestation was decreased than Ubx wildtype larvae. Further, I found evidence that the expression of specific lncRNAs could be controlled by Ubx upon wasp infestation in hemocytes. To understand the mechanism underlying Ubx function, the expression of Ubx was restricted via the CRISPR/Cas9 and UAS-Gal4 system using Srp-Gal4 as blood specific driver, and shRNA fly lines targeting the lncRNAs were generated. The Drosophila hematopoiesis model would provide insights into an alternative function of Ubx in the process of lamellocyte differentiation via lncRNAs.|연구배경 : Ubx는 homeobox gene으로써 개체의 기관 발생 과정에서 정교하게 조절되며, Ultrabithorax protein을 코딩한다. 최근 Drosophila melanogaster의 혈구세포에 대한 single-cell sequencing 결과에 따르면, 이러한 Ubx가 혈구세포 내에도 높은 수준으로 발현하고 있는 것이 확인되었다. UBX immunohistochemistry로도 혈구세포 내의 UBX protein이 확인되었고, Drosophila melanogaster larva에서 UBX의 over-expression이 melanotic tumor를 유도한다는 연구가 있었다. Melanotic tumor는 parasitoid wasp에 대한 cellular immunity의 결과로 알려져 있으므로, Drosophila melanogaster 의 혈구세포 Plasmatocyte가 cellular response에 따라 Lamellocyte(LM)로 분화하는 과정에서 UBX 및 관련된 lncRNAs가 어떤 기능을 갖는지 확인해보기로 했다.

연구방법 : 초파리 3rd larva의 혈구세포 내 UBX 발현 확인, blood specific Ubx knock-down 모델의 wasp infestation에 대한 LM 분화 양상 확인, Immune challenge를 준 뒤 혈구세포 내 발현이 증가하면서 UBX binding site를 갖는 lncRNAs들을 qPCR으로 확인, 해당 lncRNAs의 blood-specific shRNA interference를 이용한 knock-down 3rd larva 모델을 제작하여 lncRNAs K.O.시 LM 분화 양상 확인