<i>Kras</i>-4A expression is highly controlled by <i>Pas1</i> locus in normal lung.

<p>(a) Genetic linkage analysis of expression levels (square root transformed) of two <i>Kras</i> transcripts in 111 untreated ABF4 mice showed that the <i>Kras</i>-4A isoform was strongly linked to the <i>Pas1</i> locus (LOD score = 23.2) whereas the <i>Kras</i>-4B isoform showed a weaker linkage (LOD score = 4.1). Horizontal line at LOD = 2.13 marks the threshold for significance. Tick marks show the position, in a recombinational map, of the nine genotyped markers spanning from chromosome 6 position 96.7 Mb to 148.3 Mb. (b, c) Expression levels of <i>Kras</i>-4A and -4B in normal lung tissue, by genotype for the 37-bp insertion mutation common to both isoforms. The A/J-derived susceptible allele is negative (-) for the insertion whereas the C57BL/6 allele is positive (ins); 30 mice were -/-, 52 ins/-, and 29 ins/ins. (b) For <i>Kras</i>-4A, <i>P</i> = 9.7×10⁻¹⁴, ANOVA. Tukey's test for multiple comparisons, *<i>P</i> = 0.01, ***<i>P</i> = 7.4×10⁻¹⁴ vs. -/-. (c) For <i>Kras</i>-4B, <i>P</i> = 9.7×10⁻⁵, ANOVA. Tukey's test for multiple comparisons, **<i>P</i> = 1.5×10⁻⁴ vs. -/-. Values are means and SE.