Journal: The Journal of Neuroscience

Article Title: Expression of Neuregulins and their Putative Receptors, ErbB2 and ErbB3, Is Induced during Wallerian Degeneration

doi: 10.1523/JNEUROSCI.17-05-01642.1997

Figure Lengend Snippet: Identification of neuregulin splice variants expressed in axotomized sciatic nerve and the corresponding neuronal populations. A, Poly(A+) RNA was isolated from a pool of surgically transected sciatic nerve distal to the site of transection collected 16 hr, 3 d, and 7 d postinjury and a pool of L4, L5, and L6 dorsal root ganglia and lumbar spinal cord collected 7 and 10 d postaxotomy. Each RNA pool was reverse-transcribed to cDNA with random hexamer primers and used as templates for PCR with primers, the positions of which are indicated byarrows (modified from Ben-Baruch and Yarden, 1994). Distinctly different subsets of neuregulin splice variants were identified in axotomized sciatic nerve as opposed to the regions of the nervous system projecting axons into this same structure. Regions encompassed by these cDNAs include the EGF-like common domain (EGF), EGF-like variable domains (α or β), the juxtamembrane domains (numbers 1–4), and the transmembrane domain (TM). Note that splice variants with a “3” juxtamembrane domain terminate within the juxtamembrane domain (indicated by a dark bar at the C terminus). Ratios beneath each juxtamembrane domain indicate the number of times a clone with each α/β-juxtamembrane combination was isolated relative to the number of clones generated with primers “A” and “B.” Ratios in parenthesesindicate the same values for clones generated using the “A” primer in combination with “C” (4 juxtamembrane-specific) or “D” (3 juxtamembrane-specific) reverse primers. B, Schematic representation of currently known members of the GGF and SMDF neuregulin subfamilies. Although the encoded proteins contain domains in common [e.g., the EGF-like common domain (EGF)], each NRG subfamily is distinguished from one another by unique N termini [represented by SP (signal peptide) andKringle for GGF and the SMDF N terminus (Apolar) above]. Only truncated and presumably secreted (β3) variants have been described previously for GGF (Marchionni et al., 1993) and SMDF (Ho et al., 1995). In contrast, the clones described in this work represent transmembrane precursors (β1a variants) of SMDF and GGF; the presence of all domains illustrated has been confirmed by sequence analysis. These transmembrane precursors may either be cleaved to release soluble factor (Burgess et al., 1995) or potentially remain embedded in the membrane to mediate juxtacrine interactions (Bosenberg and Massague, 1993). Domains not defined above are as follows:Ig-like, Immunoglobulin-like; Glyco, glycosylation region; β, EGF-like β variable; 1 and3, juxtamembrane domains; Cytoplasmic, cytoplasmic domain common to all neuregulin transmembrane precursors;a, one of three potential neuregulin C termini.

Article Snippet: Truncated rat NRGα2 representing the EGF-like and juxtamembrane domains (rNRGα2 168–240 ) was produced using the bacterial expression vector pSLC151, which contains sequence encoding the indicated amino acids under the control of the T7 lac promoter in pET22b(+) (Novagen).

Techniques: Isolation, Random Hexamer Labeling, Modification, Clone Assay, Generated, Sequencing