Elements in the 5' flanking sequences of the mouse low-affinity NGF receptor gene direct appropriate CNS, but not PNS, expression in transgenic mice

Abstract

We have initiated a characterization of the cis-acting regulatory elements of the murine low-affinity NGF receptor (p75NGFR) gene. Despite studies in cultured cells that suggest the p75NGFR promoter is constitutive, a detailed analysis of this promoter in five lines of transgenic mice demonstrated a high degree of cell-type specificity: 8.4 kb of 5′ flanking sequence directs expression of a lacZ reporter to retinal and CNS neurons normally expressing p75NGFR. A transgene with 470 bp of 5′ flanking sequence is also expressed in the CNS, but its regulation is aberrant, with a loss of basal forebrain expression. In non-neural tissues, both transgenes were expressed only in the testis, kidney, anterior pituitary, and pancreatic islets; with the exception of the renal pattern of expression, transgene activity was confined to appropriate cells within these tissues. In contrast, although expression of both transgenes was prominent in adrenal medulla and gastrointestinal myenteric neurons, neither construct was active in several sensory or sympathetic ganglia that strongly express the endogenous p75NGFR gene, indicating that genetic elements necessary for expression in these neurons are not present in these promoter sequences. In addition, neither transgene was activated in Schwann cells during Wallerian degeneration of sciatic nerve. We conclude that regulation of the p75NGFR gene is complex, with the first 470 bp of 5′ flanking sequence sufficient for expression in enteric and CNS neurons and additional elements within the first 8.4 kb of 5′ flanking sequence required for restriction to appropriate CNS neurons. Further regulatory elements are possibly required for expression in at least some sensory and sympathetic neurons in the PNS and in Schwann cells. To identify potential regulatory elements in the 470 bp of 5′ flanking sequence from the smaller transgene, we compared the sequences of equivalent regions from the mouse, rat, and human p75NGFR genes. This “phylogenetic footprint” identified conserved motifs potentially important for the regulation of this gene in the CNS.

Commentary: Regulating proNGF Action: Multiple Targets for Therapeutic Intervention

“…The p75 promotor resembles a housekeeping gene, with high GC content, multiple Sp1 binding sites, but no TATA or CAAT elements (Sehgal et al 1988; Patil et al, 1990). A transgenic approach has been undertaken to evaluate p75 transcriptional regulation (Huber and Chao, 1995, Carroll et al, 1995); in one study, mice harboring 4kb of 5’ sequence of human p75 and the human p75 cDNA as a minigene exhibited expression by mesenchymal cells during development, mimicking endogenous expression (Huber and Chao, 1995). In addition, this p75 minigene was induced following sciatic nerve injury, although expression in uninjured peripheral neurons was lacking.…”

“…In addition, this p75 minigene was induced following sciatic nerve injury, although expression in uninjured peripheral neurons was lacking. In a second approach, analysis of a 8.4kb murine p75 promotor, using a lacZ reporter, documented appropriate expression in peripheral neurons and the retina, but no induction in Schwann cells during Wallerian degeneration (Carroll et al, 1995). Collectively, these observations suggest that multiple promoter elements exist, and that injury-response elements that regulate neuronal, but not glial expression are encoded within the proximal 4kb of the promoter.…”

β43′: An Enhancer Displaying Neural-Restricted Activity Is Located in the 3′-Untranslated Exon of the Rat Nicotinic Acetylcholine Receptor β4 Gene

“…Transgenic mice studies have shown, however, that positive modulation of transcription resulting from the binding of factors to cell-or region-specific enhancers is also required for controlling the varied patterns of transcription in the nervous system (Tuggle et al, 1990;Whiting et al, 1991;Zimmerman et al, 1994). This is also evident from studies with transgene constructs in which the deletion of relatively large fragments of DNA flanking promoter regions results in loss of transgene expression in specific neural cell populations (Vandaele et al, 1991;Min et al, 1994;Carroll et al, 1995). An example of an enhancer that directs expression to particular populations of neurons is the gonadotropin-releasing hormone gene enhancer (Whyte et al, 1995).…”

The murine Y1 receptor 5′ upstream sequence directs cell‐specific and developmentally regulated LacZ expression in transgenic mice CNS

“…One possibility is that independently acting cis information that direct expression in the periphery are positioned elsewhere in the gene. This is reminiscent of p75 NGFR gene expression regulation, where a 8.4‐kb 5′ flanking region is capable of directing spatially appropriated expression in the CNS but not in PNS neurons (Carrol et al . 1995).…”