Analysis of a new allele of limb deformity (ld) reveals tissue- and age-specific transcriptional effects of the Ld Global Control Region

Abstract

The mouse limb deformity (ld) phenotype is characterized by developmental failure of distal limb structures often associated with renal anomalies. It is caused by loss of the BMPantagonist Gremlin in the limb buds, either through mutation of Grem1, or by loss of a transcriptional global control region (GCR) located in the neighboring Fmn1 gene. In this report, we describe a new allele of ld due to complete deletion of Fmn1, including its GCR. Unlike many other ld strains, these mice are viable and fertile as homozygotes. As expected, this genomic deletion causes loss of Gremlin in the developing limb buds, but effects in other tissues are variable. Specifically, Grem1 expression is retained in the developing lung and kidney, whereas expression is lost from the corresponding adult tissues. In contrast, expression in the brain appears to be unaffected by loss of the GCR. To provide information about long-range transcriptional effects of this region, effects of the deletion on the transcription of neighboring genes were also investigated. This analysis revealed that alterations in neighboring genes do occur, but only in a limited fashion. These data indicate that the predominant effect of the Ld GCR is to activate the expression of Grem1 in the developing limb buds, although it may serve a minor role in longrange transcriptional effects that extend beyond Fmn1 and Grem1.

Genomic rearrangements of the GREM1-FMN1 locus cause oligosyndactyly, radio-ulnar synostosis, hearing loss, renal defects syndrome and Cenani-Lenz-like non-syndromic oligosyndactyly

“…His phenotype is highly reminiscent of the ld mice with oligosyndactyly, radio-ulnar synostosis and renal aplasia (figure 1A–D). The phenotypic abnormalities in this individual are similar to those of animal models in which the function of Grem1 was abrogated, thus resulting in an abnormal m-e interaction during limb and metanephric kidney organogenesis 4 5 7–9 12 13. In addition he has hearing loss, which has not yet been observed in the animal model.…”

“…The ld phenotype is autosomal recessively inherited and characterised by distinct reduction defects of the digit rays, complete radioulnar synostosis, missing fibulae, and variable renal defects 11. These abnormalities are most likely a result of disturbed function of Grem1 protein in the developing limbs due to homozygous Grem1 mutations or loss/rearrangements of a limb bud specific Grem1 transcriptional global controlling region (GCR) within the Fmn1 gene 9 12 13. The importance of Grem1 in limb development is further supported in that its over-expression in chick limb primordia results in truncations of distal autopod elements and syndactyly 14 15.…”

“…4 9 12 13 Therefore, the coding part of GREM1 gene was directly sequenced in the 15 patients in whom no causal CNVs were detected by the array CGH screening (supplemental data). No mutations were found.…”

Formins in development: Orchestrating body plan origami

“…These studies suggest that the ld phenotypes are caused not by loss of Fmn1 protein, but by loss of a region essential for Gremlin expression. A study examining deletion of the Fmn1 gene supports this hypothesis, and suggests that the renal phenotypes reported in the isoform-specific Fmn1 knockout studies above may not be a loss-of-function phenotype, but are rather due to a dominant negative effect [68]. The recent creation of a knock-in mouse containing an enhanced green fluorescence protein (EGFP) fused to Fmn1-Isoform IV has provided new insight into the cellular function of Fmn1 [69].…”

3-Dimensional Imaging Modalities for Phenotyping Genetically Engineered Mice

“…It has been used to identify skeletal abnormalities in Pthlh 94 (PTHrP) null mice, as illustrated in Figs. 7–9, and osteopotentia (AI848100)-mutant mice, 75 limbs of Ank mutant mice, 30 and Grem1 (ld1LSK) mutant mice, 69 as well as abnormalities in sacral spine of Mll Ptd/Wt mice. 26 It has also been useful for identifying cranial abnormalities in Zmpste24 -deficient mice, 20 Tg( Col2a1 - Map2k1) 1 (MEK1) mutant skulls, 11 Fgfr2 CLR/ + (C342Y) mutants, 29 and Fgfr2 +/ P253R mutant mice.…”