Figure 2.

mir-138-1 is the predominant locus transcribed in SC. (A) Schematic representation of the microRNA allele. A promoter-less lacZ reporter with an internal ribosome entry site (IRES) with a polyA (pA) signal, β-actin-driven neomycin selection marker with a pA signal, and a microRNA stem-loop flanked by loxP sites were targeted into the microRNA locus. The mice can be crossed with either germline- or tissue-specific Cre transgenic mice. We crossed mir-138-1 mice and mir-138-2 mice with germline deleter β-actin::Cre⁺ mice to produce mice with a lacZ-tagged deleted allele that lacked the β-actin promoter-neomycin casette (del). (B) Teased sciatic nerves of heterozygous lacZ-tagged mir-138-1^del/wt mice and heterozygous lacZ-tagged mir-138-2^del/wt mice at newborn and P14, stained with Xgal (blue) and Nuclear Fast Red (pink/ light red) (N ≥ 3). Arrow heads point to SC with oval-shaped nuclei. Insert shows one SC at high magnification. (C) miR-138 quantitative RT-PCR of P14 mir-138-1^del/del and mir-138-2^del/del sciatic nerves. miR-138 level is 28 fold lower in the sciatic nerves of the mir-138-1^del/del homozygous mutants than the controls (N ≥ 3, p = 0.0019), while miR-138 level in the mir-138-2^del/del homozygous mutants does not significantly differ from the controls (***p < 0.005).