An inversion involving the mouse Shh locus results in brachydactyly through dysregulation of Shh expression
Michael Niedermaier, … , Paul B. Selby, Stefan Mundlos
Michael Niedermaier, … , Paul B. Selby, Stefan Mundlos
Published April 1, 2005
Citation Information: J Clin Invest. 2005;115(4):900-909. https://doi.org/10.1172/JCI23675.
View: Text | PDF
Article Bone biology

An inversion involving the mouse Shh locus results in brachydactyly through dysregulation of Shh expression

Abstract

Short digits (Dsh) is a radiation-induced mouse mutant. Homozygous mice are characterized by multiple defects strongly resembling those resulting from Sonic hedgehog (Shh) inactivation. Heterozygous mice show a limb reduction phenotype with fusion and shortening of the proximal and middle phalanges in all digits, similar to human brachydactyly type A1, a condition caused by mutations in Indian hedgehog (IHH). We mapped Dsh to chromosome 5 in a region containing Shh and were able to demonstrate an inversion comprising 11.7 Mb. The distal breakpoint is 13.298 kb upstream of Shh, separating the coding sequence from several putative regulatory elements identified by interspecies comparison. The inversion results in almost complete downregulation of Shh expression during E9.5–E12.5, explaining the homozygous phenotype. At E13.5 and E14.5, however, Shh is upregulated in the phalangeal anlagen of Dsh/+ mice, at a time point and in a region where WT Shh is never expressed. The dysregulation of Shh expression causes the local upregulation of hedgehog target genes such as Gli1-3, patched, and Pthlh, as well as the downregulation of Ihh and Gdf5. This results in shortening of the digits through an arrest of chondrocyte differentiation and the disruption of joint development.

Authors

Michael Niedermaier, Georg C. Schwabe, Stephan Fees, Anne Helmrich, Norbert Brieske, Petra Seemann, Jochen Hecht, Volkhard Seitz, Sigmar Stricker, Gundula Leschik, Evelin Schrock, Paul B. Selby, Stefan Mundlos

×

Figure 5

Options: View larger image (or click on image) Download as PowerPoint
Shh expression in Dsh/+ limbs. (A) Section in situ hybridization at E13....
Shh expression in Dsh/+ limbs. (A) Section in situ hybridization at E13.5 and E14.5 showing strong expression of Shh in the developing distal digits in Dsh/+ but not in WT limbs. Note that expression is restricted to the anlagen of the phalanges (arrowheads). At E14.5, expression is strongest in the perichondrium of the proximal phalanx. (B) Pthlh is strongly overexpressed in Dsh/+ throughout the entire phalangeal anlagen, whereas it is restricted to the ends of the anlagen in the WT. Note overlap with Shh expression as shown in (A). (C) Expression of Ihh in WT metacarpals and phalanges (P). In contrast, Ihh is not expressed in the phalangeal anlagen of Dsh/+ limbs. (D) Immunohistochemistry with an antibody recognizing Hh protein shows restricted staining in prehypertrophic chondrocytes in the WT and Dsh/+ metacarpals and in WT phalanges corresponding to Ihh, but diffuse staining throughout the phalangeal anlagen in the mutant (large arrow) and in the perichondrium (PC) corresponding to Shh protein. (E and F) Quantitative RT-PCR of Shh (E) and Pthlh (F) mRNA in WT and Dsh/+ limbs at E10.5–E14.5. Bars represent levels (± SD) of Shh expression relative to WT E10.5 and Pthlh expression relative to WT E11.5. Magnification, ×50 (A–C), ×100 (D).