Assignment1 of DLK1 to human chromosome band 14q32 by in situ hybridization

DLK1 (delta [Drosophila]-like 1) encodes dlk, a transmembrane protein member of the EGF-like homeotic family. Members of this family participate in cell-to-cell interactions that control cell fate during differentiation. The dlk protein contains six EGF-like repeats in its extracellular domain that are highly homologous to similar domains of the Drosophila protein Delta (Laborda et al., 1993) and other EGF-like homeotic protein family members. dlk also contains a unique transmembrane domain and a short intracellular region. pG2, FA-1 (Fetal Antigen 1), Pref-1 (Preadipocyte factor 1), and dlk have all been shown to be identical or polymorphic products of a single gene (Lee et al., 1995). dlk has also been called SCP-1 (stromal cell derived protein 1) and ZOG protein (Halder et al., 1998). The functional importance of dlk in the control of cellular differentiation has been shown in several cell types, including small cell lung cancer cell lines (Laborda et al., 1993), preadipocytes (Smas and Sul, 1993), immune stem cells (Moore et al., 1997) hematopoietic stromal cells and B lymphocytes (Bauer et al., 1998), and adrenal glomerulosa cells (Halder et al., 1998). Chromosome mapping of this gene may be important to explore whether gene deletion or duplication may be associated with diseases or defaults in embryonic development. Materials and methods


Rationale and significance
DLK1 (delta [Drosophila]-like 1) encodes dlk, a transmembrane protein member of the EGF-like homeotic family. Members of this family participate in cell-to-cell interactions that control cell fate during differentiation. The dlk protein contains six EGF-like repeats in its extracellular domain that are highly homologous to similar domains of the Drosophila protein Delta (Laborda et al., 1993) and other EGF-like homeotic protein family members. dlk also contains a unique transmembrane domain and a short intracellular region.
pG2, FA-1 (Fetal Antigen 1), Pref-1 (Preadipocyte factor 1), and dlk have all been shown to be identical or polymorphic products of a single gene (Lee et al., 1995). dlk has also been called SCP-1 (stromal cell derived protein 1) and ZOG protein (Halder et al., 1998). The functional importance of dlk in the control of cellular differentiation has been shown in several cell types, including small cell lung cancer cell lines (Laborda et al., 1993), preadipocytes (Smas and Sul, 1993), immune stem cells (Moore et al., 1997) hematopoietic stromal cells and B lymphocytes (Bauer et al., 1998), and adrenal glomerulosa cells (Halder et al., 1998). Chromosome mapping of this gene may be important to explore whether gene deletion or duplication may be associated with diseases or defaults in embryonic development.

Materials and methods
DLK1 clones from a human P1 genomic library (Genome Systems Inc., St. Louis MO) were selected by using a PCR primer pair that amplifies a fragment of exon V of DLK1. The sequence of the primers and the conditions of the PCR amplification have been previously published (Lee et al., 1995). The genomic clones identified were characterized as corresponding to DLK1 by sequencing, restriction enzyme digestions and Southern blot hybridization. Genomic fragments of around 50 kb in length were used for FISH mapping, performed by Genome Systems Inc. (St. Louis MO) according to standard procedures (Shi et al., 1997). DNA was labeled with digoxigenin dUTP by nick translation. Labeled probe was mixed with sheared human DNA and hybridized to normal metaphase chromosomes derived from PHA-stimulated peripheral blood lymphocytes. Specific hybridization signals were detected by means of antidigoxigenin antibodies followed by counterstaining with DAPI. Chromosome identity was confirmed in dual-labeling experiments using the DLK1 probe and probes specific for the centromeric region of the chromosomes (Fig. 1).

Probe name: 12216
Probe type: genomic DNA fragment Insert size: 50 kb Vector: P1 bacteriophage Proof of authenticity: DNA sequencing, restriction enzyme mapping, Southern blot hybridization with cDNA probe.

Results
Mapping data of human DLK1 Location: 14q32 Number of cells examined: 80 Number of cells with specific signal: 1(0), 2(5), 3(4) 4(71). Most precise assignment: 14q32.33. Location of background signals (sites with 1 2 signals): none observed Fig. 1. FISH mapping of human DLK1 with probe 12216. The specific signals detected on chromosome 14 are indicated by arrows. The specificity of the location was confirmed by co-hybridization with a biotin labeled probe specific for the centromere of chromosome 14 and 22. Observation of specifically labeled chromosomes 14 demonstrated that DLK1 is located at band 14q32. The picture was generated by Genome Systems Inc.