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The GLI protein family is involved in several key developmental processes in both vertebrates and invertebrates. The Drosophila GLI protein, Cubitus interuptus (Ci), regulates segment polarity and wing and leg development. In vertebrates, the GLI proteins control neural, lung, bone and gut development1. In the nematode Caenorhabditis elegans, the GLI family member TRA-1 is necessary for normal sexual development2,3. GLI, Ci and TRA-1 each contain five zinc-finger domains and bind the identical DNA sequence. Previous analyses are consistent with these proteins being transcription factors4,5. Here we show that TRA-1 can act post-transcriptionally to govern gene activity. Our results indicate that the binding of TRA-1 to the 3′ untranslated region oftra-2 regulates the export of tra-2 messenger RNA from thenucleus. The fact that TRA-1 is part of a conserved family ofproteins raises the possibility that GLI family members are both transcriptional and post-transcriptional regulators of gene expression.

IT is well known that the neonatal rat brain contains relatively little serotonin1,2 and that the level of this amine increases slowly with age. Karki et al.3 have shown that the enzymes mediating the synthesis and oxidation of serotonin are also low in the immature rat brain, and increase thereafter with growth of the animal. The aforementioned authors suggest that the low levels of indolamines in the rat brain at birth can be attributed to a deficiency of the binding or storage system, and are not a reflexion of the insufficiency of the enzyme systems. Schanberg and Giarman4,5 have shown that endogenous brain serotonin distributes itself between the particulate matter of brain homogenates and the supernatants, and that this relationship is susceptible to alteration by drugs. It was, therefore, of interest to investigate the sub-cellular distribution of serotonin in the developing rat brain and to determine whether it will parallel other maturational changes.

THE mammalian foetus synthesizes a serum α-globulin, called α-foetoprotein, which is not found in the adult of the species1–7. Although interspecies structural differences among the α-foetoproteins have been noted4–7, the protein of each species appears to be a homologue of foetuin, or bovine α-foetoprotein5,7. Synthesis of serum α-foetoprotein has been shown to occur in the liver in both the rat foetus8,9 and the human embryo9, and in the yolk sac of the rat9. The cells responsible for this synthesis are not known, however, and it has been suggested that the haematopoietic tissue of the liver may be the site of synthesis8. In the present investigation, the cellular distribution of α-foetoprotein in organs of the rat foetus was investigated by means of the fluorescent antibody method.

Inouye, Kataoka and Shinagawa1 have recently criticized, by implication, my work on the sub-cellular distribution of 5-hydroxytryptamine (HT) in guinea pig brain2. I do not agree that my assays were significantly interfered with by substance P. The reasons for this are as follows.