Article Figures & Data
Figures
- Figure 1.
Early deletion of Ldb1 using Foxg1Cre results in reduced telencephalic size and disrupted telencephalic midline patterning. A, B, Whole brains and coronal sections at E12.5 from control (A) and Foxg1Cre;Ldb1lox/lox mutants (B) reveal a greatly reduced telencephalon on loss of Ldb1. Ldb1 is expressed in the entire control telencephalon and thalamus at E12.5 (A) but is undetectable in the mutant telencephalon (B). The expression boundaries of Ldb1 in the retina (open arrowhead, B) and the diencephalon (black arrowhead, B) are consistent with the reported activity of Foxg1Cre (Hebert and McConnell, 2000). C, D, E12.5 sections from control (C) and Foxg1Cre;Ldb1lox/lox mutant (D) brains. The expression of choroid plexus marker Ttr is lost in the mutant (open arrowheads, C, D). The mutant does not express hem marker Wnt2b but displays an expanded expression of Wnt5a and Lmx1a. Lmx1a labels both hem and choroid plexus in control sections. Foxg1 is expressed in a manner complementary to Lmx1a in control and mutant sections. Black arrowheads mark the cortex-hem boundary (C, D). Dbx1 is expressed in the septum (white asterisks) and antihem (black asterisks), both of which are expanded on loss of LDB1 (C, D). Scale bars: 100 μm.
- Figure 2.
Two standard Cre drivers display differential recombination of the Ldb1 locus in the dorsal telencephalon. A–C, Expression of Ldb1 mRNA and the Ai9 reporter in E12.5 control (A), Emx1Cre;Ldb1lox/lox;Ai9 (B), and NesCre;Ldb1lox/lox;Ai9 (C) brains. A’–C’, Cartoons indicating the domain of Cre activity in the respective conditions. In each condition, Ai9 fluorescence faithfully reports Cre activity in the expected domains. However, Ldb1 expression is seen in a medio-lateral gradient in the dorsal telencephalon of Emx1Cre;Ldb1lox/lox;Ai9 embryos (B) and persists in the entire dorsal telencephalon in NesCre;Ldb1lox/lox;Ai9 brains (C). In contrast, the ventral telencephalon (vtel) and the diencephalon (black asterisk) display the expected loss of Ldb1 expression. D–F, Expression of Lhx2 mRNA and mTmG (GFP) reporter in E12.5 control (D), Emx1Cre;Lhx2lox/lox;mTmG (E), and NesCre;Lhx2lox/lox;mTmG (F) brains. Lhx2 is recombined and its expression is undetectable in the dorsal telencephalon of Emx1Cre;Lhx2lox/lox;mTmG brains, and mTmG reporter displays a complementary pattern, consistent with the activity domain for Emx1Cre (E). NesCre;Lhx2lox/lox;mTmG brains display no detectable Lhx2 expression and widespread expression of the mTmG reporter, consistent with the activity domain of NesCre (F). The control brains display autofluorescence in the green channel in the region of the choroid plexus which is an artifact. Scale bars: 100 μm.
- Figure 3.
Recombination efficiency of the Ldb1 locus improves with time in the case of Emx1Cre but not NesCre. A–C, Expression of Ldb1 mRNA in E15.5 control (A), Emx1Cre;Ldb1lox/lox (B), and NesCre;Ldb1lox/lox (C) brains at three rostro-caudal levels. Emx1Cre;Ldb1lox/lox brains display low Ldb1 expression in the dorsal telencephalon, with no medio-lateral expression gradient. White arrows in B mark a spur of Ldb1 expression consistent with the migrating interneuron stream that originates in the Ldb1-expressing ventral telencephalon. In contrast, NesCre;Ldb1lox/lox brains display robust expression in the cortical plate and in the hippocampus (black arrowheads), but the ganglionic eminences (black asterisks) and thalamus (white asterisks) appear to have lost Ldb1 expression. Scale bars: 100 μm.
- Figure 4.
LDB1 is required for patterning the dorsal thalamus. A, B, Expression of Ldb1 mRNA in E12.5 control (A) and NesCre;Ldb1lox/lox (B) brains at three rostro-caudal levels. In the mutant, Ldb1 expression is undetectable in a broad region of the dorsal thalamus of the mutant brains (black asterisks, B). C–F, Serial sections from the same brains in A, B probed for the expression of Lhx9 and Neurog2 at three rostro-caudal levels. In the mutant, the medial domain of intense Neurog2 expression (white dashed lines, C, D) expands laterally at mid and caudal levels (white asterisks, C, D). At the same levels of sectioning, Lhx9 expression, which is normally not seen in a lateral domain (solid black lines, E), expands in the mutant to fill this domain (open arrowheads, F). Scale bars: 500 μm.
- Figure 5.
The somatosensory VB nucleus is profoundly shrunken on loss of LDB1. A, B, Expression of SERT mRNA in the VB nucleus in control (ovals, A) and NesCre;Ldb1lox/lox (B) brains at three rostro-caudal levels. In the mutant, SERT expression is limited to a very narrow region in caudal sections, a severely diminished VB (open arrowhead, B). Scale bars: 500 μm.
- Figure 6.
Multiple markers reveal shrinkage of the somatosensory VB on loss of LDB1. A–F, Sections from E17.5 control (A, C, E) and NesCre;Ldb1lox/lox (B, D, F) embryos at three rostro-caudal levels. A, B, Expression of Ldb1 mRNA in E17.5 control (A) and NesCre;Ldb1lox/lox (B) brains. In the mutant, Ldb1 expression is undetectable in a broad region of the dorsal thalamus (asterisks, B), while expression in the cortical plate (black arrowheads, A, B) and hippocampus persists. C–F, Chst2 expression is seen at the perimeter of the VB nucleus (ovals, C), and Prox1 expression excludes the VB nucleus leaving a distinct negative zone (oval, E). These features are not revealed in mutant sections (D, F), in which only a small Prox1 negative domain is seen (solid line, F). Black and open arrowheads identify the PO and the dLGN, respectively, which appear to be present in both control and mutant brains. Scale bars: 500 μm.
- Figure 7.
The VB is undetectable at P0 in LDB1 mutant brains. A–C, Sections from P0 control and NesCre;Ldb1lox/lox brains. A, SERT expression reveals the VB nucleus in control brains (black outline), which is undetectable in the mutant. B, C, Chst2 and Prox1 expression is seen at the perimeter of the VB nucleus in control (black outlines), but not in mutant brains. Scale bars: 500 μm.
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