The mouse RhoH gene structure and restricted expression of RhoH in hematopoietic cells. (A) Mouse RhoH genomic locus and its mRNA. E1, E2, and E3 represent 3 individual exons. The untranslated and translated sequences are shown in filled and open boxes, respectively. (B) Alignment of the amino acid sequences of human and mouse RhoH. *Indicates identical amino acid. Bold letters indicate residues at 2 key sites critical for GTPase activity and different from those at corresponding positions in most other Rho GTPases. (C) Expression of RhoH in mouse tissues and cells assayed by RT-PCR analysis using primers P01 and P02 shown in panel A. β-Actin was used as a loading control. (D) Northern blot analysis using total RNAs from mouse hematopoietic tissues and cells and a RhoH cDNA probe shown in panel A. The ethidium bromide–stained 28S and 18S rRNAs were used as loading controls. The results shown in panels C and D are representatives of 4 experiments. (E) In situ hybridization of RhoH transcript localization in adult mouse thymus. Microscopy of frozen tissue sections hybridized with radiolabeled antisense (AS; left and middle panels) or sense (S; right panel) RhoH cDNA probes. Bright field (left panel) and dark field (middle and right panels) images are shown at 200 × original magnification. The bright field signal is black and the dark field signal is white. In the paired bright and dark field images (left and middle panels), positive signals are present in thymocytes of the thymic cortex but not in nonlymphoid cells of fibrovascular and fibroadipose tissues (arrows). Representative images from 2 experiments are shown.