Imprinting, expression, and localisation of DLK1 in Wilms tumours.
BACKGROUND
Loss of imprinting (LOI) of the H19/IGF2 domain is a common feature of Wilms tumour. The GTL2/DLK1 domain is also imprinted and is structurally similar to H19/IGF2. The question arises as to whether DLK1 also undergoes LOI in Wilms tumour, or whether the LOI mechanism is restricted to the H19/IGF2 domain.


OBJECTIVE
To investigate the imprinting status of DLK1 in Wilms tumours with IGF2 LOI. The cellular localisation of DLK1 in the tumours was also examined.


METHODS
DLK1 expression was measured by quantitative real time polymerase chain reaction (Q-PCR) in 30 Wilms tumours that had previously been classified according to whether they had IGF2 LOI, WT1 mutations, or 11p15.5 loss of heterozygosity. Allele specific expression of DLK1 was examined by direct sequencing using a DLK1 exon 5 polymorphism (rs1802710). Immunohistochemical analysis of DLK1 was performed on 13 tumours and two intralobar nephrogenic rests, in addition to two fetal kidneys and one fetal skeletal muscle sample.


RESULTS
Ten of 30 tumours were heterozygous for rs1802710 and all tumours showed retention of imprinting of DLK1. Moderate to high expression of DLK1 was detected by Q-PCR in nine of 13 tumours with myogenic differentiation. Immunohistochemical expression of DLK1 was detected in the myogenic elements.


CONCLUSIONS
LOI does not occur at the GTL2/DLK1 domain in Wilms tumour. This finding suggests that LOI at 11p15.5 does not reflect non-specific disruption of a shared imprinting mechanism. DLK1 expression in Wilms tumour might reflect the presence of myogenic differentiation, rather than an alteration of its imprinting status.
Fukuzawa
R
R
Cancer Genetics Laboratory, Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand. ryuji.fukuzawa@stonebow.otago.ac.nz
Heathcott
R W
RW
Morison
I M
IM
Reeve
A E
AE
D000483:Alleles; D044127:Epigenesis, Genetic / Q000235:genetics; D016162:Genes, Wilms Tumor; D018392:Genomic Imprinting / Q000235:genetics*; D006023:Glycoproteins / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000737:chemistry / Q000196:embryology; D007680:Kidney Neoplasms / Q000235:genetics* / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D011506:Proteins / Q000235:genetics; D062085:RNA, Long Noncoding; D012334:RNA, Neoplasm / Q000032:analysis; D009396:Wilms Tumor / Q000235:genetics* / Q000473:pathology
D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; C498907:MEG3 non-coding RNA, human; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D011506:Proteins; D062085:RNA, Long Noncoding; D012334:RNA, Neoplasm; C064045:delta protein