Abstract: The present invention provides novel methods for identifying gene expression patterns in mRNA populations. The methods are useful for determining differential gene expression among various cells or tissues, including cells or tissues of a target organism. The invention also provides methods of determining the frequency of gene expression in mRNA populations, thus providing a method of comparing gene expression frequency among various cells or tissues. The present invention also provides methods for isolating genes corresponding to tag sequences identified according to the methods of the present invention. Furthermore, sequences that are identified according to the present invention may be used to diagnose the presence of disease.

Abstract: The invention is directed to substantially purified Eph-related protein tyrosine kinases, or functional fragments thereof, having about 23 to 66 percent amino acid sequence identity in their carboxyl terminal variable regions compared to known members of the Eph subclass of tyrosine kinases. Nucleic acids encoding such Eph-related protein tyrosine kinases, vectors and host cells are also provided. The invention is also directed to a method of diagnosing cancer and determining cancer prognosis. The method includes removing a tissue or cell sample from a subject suspected of having cancer and determining the level of Eph-related protein tyrosine kinase in the sample, wherein a change in the level or activity of a Eph-related protein tyrosine kinase compared to a normal sample indicates the presence of a cancer or indicates the level of malignancy of a cancer.