FIG. 2.

Slo and the Slo exon STREX are transcribed tonotopically. Shown are the relative expression levels of both Slo and its alternatively spliced STREX exon in the low- (LF, n = 3), middle- (MF, n = 3), and high-frequency (HF, n = 4) segments of the post-hatch chicken basilar papilla as determined by qPCR. Expression levels were normalized first to 18S expression, then respectively to Slo and STREX expression levels in the LF segment. A clear tonotopic gradient can be appreciated for both Slo and STREX with expression that significantly decreased from the LF region to the HF region (one-way ANOVA, p < 0.05). The fold-change differences of LF versus MF and LF versus HF were significantly different between STREX and Slo, indicating a steeper gradient for STREX than for Slo (t tests, p < 0.05).