Growth factor that controls proliferation and cellular differentiation in the retina. Plays a key role in regulating apoptosis during retinal development. Establishes dorsal-ventral positional information in the retina and controls the formation of the retinotectal map. Functions maternally in dorsal/ventral patterning to induce the expression of the zygotic bmp2b and bmp4 genes and ventralize embryos. Zygotic expression does not appear to regulate axis specification, but instead functions to establish the integrity of the axial vessels during embryonic development. May be involved in maintaining the identity of cells of the dorsal-most neural tube and of at least a subset of neural crest cells. Homodimer; disulfide-linked. First expressed in late gastrula stage embryos (9.5 hours post fertilization (hpf)) in anterior neuroectoderm corresponding to the future dorsal part of the brain. Shortly after tailbud formation (11 hpf), expression expands to the entire neural region and is subsequently expressed in derivatives of the lateral neural plate and migrating neural crest cells, with the future midbrain and hindbrain showing strong expression. Also expressed weakly and transiently in the posterior embryo from 11.5 hpf to 15 hpf in the lateral mesoderm, and in ectoderm above the neural keel. At 14 hpf, expressed along the entire length of the embryo and starting around the 16-somite stage, expressed in the dorsal quadrant of the retina, representing the distal tip of the eye anlage. At this stage, also expressed in the hatching gland and the hypochord. At 24 hpf, expressed in the roof plate outlining the fourth brain ventricle, in the posterior hypochord, the primitive gut endoderm, the ventral tail mesenchyme, the dorsal part of the neural tube and the dorsal fin. Weakly expressed in the dorsal part of the posterior spinal cord and in blood cell precursors. Expressed both maternally and zygotically. Expressed from early cleavage stage until blastula sphere stage. Expression is then barely detectable until the end of gastrulation (tailbud stage) when expression is resumed. Adults display microphthalmia, with eyes obscured by overgrown skin and misshapen irides. Mutants at 2 weeks of age show profound alterations in the morphology of individual photoreceptor subtypes and UV cones. At later timepoints loss of normal retinal lamination is observed, together with a disorganization of Mueller glia cells. Adults, cone photoreceptors are dysmorphic and reduced in abundance. Belongs to the TGF-beta family.