Expression of multiple neuregulin transcripts in postnatal rat brains.

The distribution of neuregulin transcripts in rat brains was studied by both RNA blotting and in situ hybridization. Our data demonstrate that multiple neuregulin transcripts are expressed in neurons of the basal forebrain, the hippocampus, the diencephalon, the cerebellum, the brainstem, and the spinal cord. Developmental changes in the distribution of neuregulin transcripts were observed only in the cerebellum and the hippocampus. The intense neuregulin hybridization signals in the brainstem motor and sensory nuclei and the spinal motor neurons are suggestive of a functional involvement of neuregulins in motor and sensory systems. The expression of neuregulins in other parts of the brain also indicates that these factors are involved in a variety of central nervous system functions.

mRNAs for insulin-like growth factor-II (IGF-II) and variant IGF-II are co-expressed in human fetal ovary and uterus.

Insulin-like growth factor-II (IGF-II) is postulated to have autocrine and/or paracrine functions in developing fetal tissues, but has never been reported in human fetal reproductive organs. The forms of IGF-II found in normal human serum include a 67 amino acid form and a variant form resulting from alternate splicing of the mRNA such that Ser-29 is replaced by four other amino acid residues. We studied the expression of mRNA encoding IGF-II in human fetal ovaries and uteruses of 10, 15, 19 and 22 weeks of gestation. By reverse transcription followed by polymerase chain reaction (PCR), we identified the co-expression of two mRNAs encoding IGF-II in all developmental stages of fetal ovaries and uteruses tested. One of the PCR amplified fragments was 9 nucleotides larger than the other. The PCR amplified ovarian and uterine DNA fragments were mapped by digestion with the restriction endonucleases AvaII and PvuII and both the IGF-II fragment and the larger IGF-II fragment produced the anticipated DNA patterns by gel electrophoresis. The PCR amplified DNA fragments were cloned and sequenced to confirm that the expressed mRNAs encoded IGF-II and variant IGF-II. We conclude that IGF-II and variant IGF-II mRNA co-expression occurs in the human fetal female genital tract and that the two forms of the growth factors may have physiologic roles in reproductive tract development.