Search

OBJECTIVES--To identify, map, clone, and functionally validate a novel mouse model for impaired glucose tolerance and insulin secretion. RESEARCH DESIGN AND METHODS--Haploinsufficiency of the insulin receptor and associated mild insulin [...]

Zinc finger of the cerebellum (Zic) proteins act as classic transcription factors to promote transcription of the Foxd3 gene during neural crest cell specification. Additionally, they can act as co-factors that bind proteins from the T-cell factor/lymphoid enhancing factor (TCF/LEF) family (TCFs) to repress WNT-β-catenin-dependent transcription without contacting DNA. Here, we show that ZIC activity at the neural plate border is influenced by WNT-dependent SUMOylation. In the presence of high canonical WNT activity, a lysine residue within the highly conserved zinc finger N-terminally conserved (ZF-NC) domain of ZIC5 is SUMOylated, which reduces formation of the ZIC-TCF co-repressor complex and shifts the balance towards transcription factor function. The modification is crucial in vivo, as a ZIC5 SUMO- incompetent mouse strain exhibits neural crest specification defects. This work reveals the function of the ZF-NC domain within ZIC, provides in vivo validation of target protein SUMOylation and demonstrates that WNT-β-catenin signalling directs transcription at non-TCF DNA-binding sites. Furthermore, it can explain how WNT signals convert a broad region of Zic ectodermal expression into a restricted region of neural crest cell specification. [ABSTRACT FROM AUTHOR]

Del (13) Svea36H (De136H) is a deletion of ~20% of mouse chromosome 13 showing conserved synteny with human chromosome 5p22.1-6p22.3l6p25. 12.7 Mb of finished and annotated sequence from Del136H mouse that provides insights into mouse genome evolution is described.

The ZIC transcription factors are key mediators of embryonic development and ZIC3 is the gene most commonly associated with situs defects (heterotaxy) in humans. Half of patient ZIC3 mutations introduce a premature termination codon (PTC). In vivo, PTC-containing transcripts might be targeted for nonsense-mediated decay (NMD). NMD efficiency is known to vary greatly between transcripts, tissues and individuals and it is possible that differences in survival of PTC-containing transcripts partially explain the striking phenotypic variability that characterizes ZIC3-associated congenital defects. For example, the PTC-containing transcripts might encode a C-terminally truncated protein that retains partial function or that dominantly interferes with other ZIC family members. Here we describe the katun (Ka) mouse mutant, which harbours a mutation in the Zic3 gene that results in a PTC. At the time of axis formation there is no discernible decrease in this PTC-containing transcript in vivo, indicating that the mammalian Zic3 transcript is relatively insensitive to NMD, prompting the need to re-examine the molecular function of the truncated proteins predicted from human studies and to determine whether the N-terminal portion of ZIC3 possesses dominant-negative capabilities. A combination of in vitro studies and analysis of the Ka phenotype indicate that it is a null allele of Zic3 and that the N-terminal portion of ZIC3 does not encode a dominant-negative molecule. Heterotaxy in patients with PTC-containing ZIC3 transcripts probably arises due to loss of ZIC3 function alone.

The epidermal growth factor (EGF) superfamily comprises a diverse group of proteins that function as secreted signaling molecules, growth factors, and components of the extracellular matrix, many with a role in vertebrate development. We have isolated a novel mammalian gene encoding an EGF-related protein with a CUB (C1s-like) domain that defines a new mammalian gene family. The Scube1(signal peptide-CUB domain-EGF-related 1) gene was isolated from a developing mouse urogenital ridge cDNA library and is expressed prominently in the developing gonad, nervous system, somites, surface ectoderm, and limb buds. We have mapped Scube1to mouse chromosome 15 and show that it is orthologous to a human gene in the syntenic region of chromosome 22q13. We discuss the possible functions of this novel gene and its role in heritable disease in light of these data.

We have recently reported the preliminary characterisation of a novel EGF-related gene, Scube1(signal peptide-CUBdomain-EGF-related, gene 1), that is expressed prominently in the developing gonad, nervous system, somites, surface ectoderm and limb buds of the mouse. Here we describe the expression pattern of a closely related gene, Scube2 (also known as Cegp1), which maps to the distal region of mouse chromosome 7. Scube2transcription is restricted to the embryonic neurectoderm but is also detectable in the adult heart, lung and testis.