Detection of genes regulated by Lmx1b during limb dorsalization

Abstract

Lmx1b is a homeodomain transcription factor that regulates dorsal identity during limb development and Lmx1b knockout (KO) mice develop nearly symmetrical ventral‐ventral limbs with hypoplastic scapulae. Currently, downstream targets of Lmx1b within dorsal mesoderm that impart the limbs' unique dorsal asymmetry are unknown. To identify genes targeted by Lmx1b, we compared gene arrays from Lmx1b KO and wild type (WT) mouse limbs during limb outgrowth and patterning, i.e., 11.5, 12.5, and 13.5 days post coitum (dpc). Real‐time PCR confirmed microarray results and whole mount in situ hybridization was used to localize and verify differential dorsal‐ventral expression. Microarray analysis identified 23 targets differentially expressed in all three arrays. Real‐time PCR confirmed 17 up‐regulated and 2 down‐regulated targets. Whole mount in situ hybridization of WT 12.5 dpc embryos demonstrated a dorsal‐ventral asymmetric pattern for the validated targets, further categorized as skeletal, soft tissue or other. Skeletal targets, including Emx2, Matrilin1 and Matrilin4, demonstrated a loss of scapular expression in the Lmx1b KO mice. Soft tissue targets which demonstrated dorsal mesodermal staining in WT were drastically reduced in KO limbs. This study provides the most comprehensive characterization of skeletal and soft tissue genes regulated by Lmx1b during limb development to date. Our data also suggest targets which Lmx1b may augment to ensure proper scapular development. Further studies are warranted to determine the mechanism of Lmx1b target regulation during limb dorsalization. NIH HD39421

Muscle-type Identity of Proprioceptors Specified by Spatially Restricted Signals from Limb Mesenchyme

“…However, the sensory profile of cdh13 is unaltered in mice in which NT-3 is ectopically expressed in all limb muscles (data not shown), arguing against the sufficiency of muscle NT-3 as a cdh13 inducer. The secreted cerebellin (Cbln) family contains candidates for induction of cdh13 and sema5a in proprioceptors, given their restricted expression by dorsal limb mesenchyme, and down-regulation from limb mesenchyme in Lmx1b −/− mice (Feenstra et al, 2012; Haddick et al, 2014). It is also possible that mesenchymal cues responsible for guiding motor axons have a dual role in specifying proprioceptor muscle-type identity, in that ephrins, glial derived neurotrophic factor (GDNF) and netrin-1 are expressed in a restricted manner by dorsal or ventral limb mesenchyme and regulate the dorso-ventral choice of motor axons (Stifani, 2014, Poliak et al, 2015).…”

Pigeon foot feathering reveals conserved limb identity networks

“…We identified a set of 978 genes that are differentially expressed between FL and HL at HH21, HH25, and/or HH29 ("FL/HL" gene set; Table 1, Supplemental Figure 1, and Supplemental Table 1). Within the FL/HL gene set, only 12 genes are strongly enriched (defined here as an absolute value Log2FC > 2) in a FL-or HL-specific manner ( Figure 1F), all of which are TFs that have been implicated in vertebrate limb development to varying degrees (Takeuchi et al, 1999, Szeto et al, 1999, Logan and Tabin, 1999, Zakany and Duboule, 2007, Tarchini et al, 2006, Capellini et al, 2006, Boulet and Capecchi, 2004, Wellik, 2003, Davis and Capecchi, 1994, Capellini et al, 2010, Narkis et al, 2012, Feenstra et al, 2012. In contrast, the majority (86-95%) of differentially expressed genes changed less than 2-fold (Log2FC < 1) between FL and HL ( Figure 1F).…”

Steroid-resistant nephrotic syndrome as the initial presentation of nail-patella syndrome: a case of a de novo LMX1B mutation

“…LMX1B is expressed in the dorsal mesenchyme of developing vertebrate limbs and plays a critical role in the patterning of the dorsal-ventral axis [7]. Once the dorsal-ventral axis is established, LMX1B activates the expression of a number of dorsalizing genes, suppresses the expression of ventralizing genes, and modulates the development of dorsal distal limb structures such as nails and patellas [4].…”