Brian Hall is the son of Doris Garrad and Harry Hall, and was born in Port Kembla, NSW Australia, on 28 October 1941. He attended the University of New England in Armidale NSW, graduating in 1963 with a BSc in zoology, in 1965 with a BSc (Honors) in zoology, and in 1968 with a PhD in zoology. His PhD thesis, undertaken under the supervision of Patrick D. F. Murray, FAA was on the differentiation of bone and secondary cartilage in chicken embryos. Hall's laboratory research focuses on developmental biology and evolutionary developmental biology (evo-devo), especially of the vertebrate neural crest and skeletal tissues that arise from neural crest cells.
Neurocristopathies are a class of pathologies in vertebrates, including humans, that result from abnormal expression, migration, differentiation, or death of neural crest cells (NCCs) during embryonic development. NCCs are cells derived from the embryonic cellular structure called the neural crest. Abnormal NCCs can cause a neurocristopathy by chemically affecting the development of the non-NCC tissues around them. They can also affect the development of NCC tissues, causing defective migration or proliferation of the NCCs. There are many neurocristopathies that affect many different types of systems. Some neurocristopathies result in albinism (piebaldism) and cleft palate in humans. Various pigment, skin, thyroid, and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract, and tumors can be classified as neurocristopathies. This classification ties a variety of disorders to one embryonic origin.
Early in the process of development, vertebrate embryos develop a fold on the neural plate where the neural and epidermal ectoderms meet, called the neural crest. The neural crest produces neural crest cells (NCCs), which become multiple different cell types and contribute to tissues and organs as an embryo develops. A few of the organs and tissues include peripheral and enteric (gastrointestinal) neurons and glia, pigment cells, cartilage and bone of the cranium and face, and smooth muscle. The diversity of NCCs that the neural crest produces has led researchers to propose the neural crest as a fourth germ layer, or one of the primary cellular structures in early embryos from which all adult tissues and organs arise. Furthermore, evolutionary biologists study the neural crest because it is a novel shared evolutionary character (synapomorphy) of all vertebrates.
Julia Barlow Platt studied neural crests in animal embryos and became involved in politics in the US during the nineteenth and twentieth centuries. She researched how body and head segments formed in chicks (Gallus gallus) and spiny dogfish (Squalus acanthias). Platt observed that in the mudpuppy (Necturus maculosus), the coordinated migration of neural crest cells in the embryo produced parts of the nervous system, bones, and connective tissues in the head. Platt's research indicated that the neural crest functioned like a germ layer, it challenged existing theories of what sorts of tissues arose from each of an embryo's germ layers, and it described early developmental stages of the nervous system.
This diagram shows how NCCs migrate differently in rats, birds and amphibians. The arrows represent both chronology of NCCs migration and the differential paths that NCCs follow in different classes of animals. The solid black portion of each illustration represents the neural crest, and the large black dots in (c) and in (f) represent the neural crest cells. The speckled sections that at first form a basin in (a) and then close to form a tube in (f) represent the neural ectoderm. The solid white portions represent the epidermal ectoderm.