Figure 1.

Massively parallel signature sequencing (MPSS) A: The genomic locations and structures of Entpd1, Entpd2, Entpd3 and Entpd8 (genes encoding NTPDases 1, 2, 3 and 8) are shown. Gene chromosomal positions were obtained from the Build 33 assembly by NCBI. Exons are indicated by filled boxes, and the position and direction of the signature tags are indicated by arrowheads. As expected from the cloning procedures, each signature is associated with the 3′ most DpnII site of the coding sequence. B: Histograms display the abundance of each signature, expressed as transcripts per million (tpm), in libraries constructed from mRNA isolated from either taste bud enriched tissue (TB), lingual epithelium devoid of taste buds (LE), or inner ear derived tissues including the Organ of Corti (Cr), stria vascularis (SV) and otic vesicle (OV). Entpd2 mRNA is represented 9 times per million in the TB library (arrowhead below bar graph) but is not represented in the LE library, suggesting selective Entpd2 expression in taste buds. Taken together with the absence of Entpd1, Entpd3, and Entpd8 in the TB library, these results support that NTPDase2 is the primary ecto-ATPase expressed in taste buds. For sake of comparison, the taste receptor T1R2 is represented 10 tpm in the TB library and is absent in the LE library (data not shown).