family involved in the production of bone and
cartilage, and important regulators of dorsoventral patterning.
BONE MORPHOGENETIC PROTEINS Molecules of the TGF- family involved in the production of bone and
cartilage, and important regulators of dorsoventral patterning.
CEREBELLAR PLATE Structure that constitutes the cerebellar primordium. It is formed by the
fusion of the rhombic lips at the midline.
CLONAL RESTRICTION Restriction of all the progeny of a given ancestor cell to a spatially
limited territory.
DOMINANT-NEGATIVE PROTEIN A mutant molecule capable of antagonizing the function of its endogenous
counterpart.
EPIBLAST The outer layer of a blastula that gives rise to the ectoderm after gastrulation.
FLOOR PLATE The neural tube has been divided in different regions. The ventral cells
closest to the midline constitute the floor plate. The dorsal cells closest
to the midline correspond to the roof plate. The alar plate (dorsal) and the
basal plate (ventral) lie between these two cell populations and are separated
by the sulcus limitans.
GAP JUNCTIONS Cellular junctions that allow the free passage of small molecules through
non-selective channels called connexons.
GASTRULA Embryo that is in the process of regionalizing into three germ layers (ectoderm,
mesoderm and endoderm).
HOMEODOMAIN-CONTAINING PROTEINS
Transcription factors with a 60 amino acid DNA-binding domain comprised
of three 
-helices.
LOCUS COERULEUS Brainstem nucleus that constitutes the main supply of noradrenaline to
the rest of the brain.
MES-METENCEPHALIC JUNCTION Refers to the narrow territory where the isthmic organizer is localized,
and should not be confused with mes-metencephalic domain, which comprises
the whole mesencephalic and metencephalic regions. Similarly, the term mid-hindbrain
domain should be understood as mes-metencephalic domain, and not as referring
to the whole midbrain and hindbrain areas.
NEUROMERES Series of swellings and constrictions along the neural tube at early stages
of embryonic development, which constitute evidence of the intrinsic segmentation
in the nervous system.
NEURULATION Morphogenetic process during which the progenitors of the nervous system
segregate from the ectoderm.
NOTOCHORD Rod-like structure of mesodermal origin found in vertebrate embryos, which
participates in the differentiation of the ventral neural tube and in the
specification of ventral neurons.
PROSENCEPHALON The most rostral of the primary vesicles that are present in the early
neural tube, which later gives rise to two secondary vesicles: telencephalon
(prospective cerebral hemispheres) and diencephalon (prospective thalamus,
hypothalamus).
PROSOMERE Each of the six subdivisions thought to compose the embryonic forebrain,
defined by their specific patterns of gene expression. Prosomeres 1–3
constitute the diencephalon, whereas prosomeres 4–6 comprise the hypothalamus
and the telencephalon.
RAPHE NUCLEI Brainstem structures that constitute the main supply of serotonin to the
rest of the brain.
RHOMBENCEPHALON The most caudal of the primary vesicles that are present in the early neural
tube, which later gives rise to two secondary vesicles: metencephalon (prospective
pons and cerebellum) and myelencephalon (prospective medulla oblongata).
RHOMBOMERE Each of seven neuroepithelial segments found in the embryonic hindbrain
that adopt distinct molecular and cellular properties, restrictions in cell
mixing and ordered domains of gene expression.
SOMITES Paired blocks of mesoderm cells along the vertebrate body axis that form
during early vertebrate development and differentiate into dermal skin, bone
and muscle.
TELEOST Group of fish with bony skeletons.
VERMIS Cerebellar structure located at the midline involved in maintaining posture
and the control of eye movement.
ZONA LIMITANS INTRATHALAMICA Embryonic structure that determines the limit between dorsal and ventral
thalamus.
