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Histology Atlas of the Developing Prenatal and Postnatal Mouse Central Nervous System, with Emphasis on Prenatal Days E7.5 to E18.5

Vivian S. Chen, James P. Morrison, Myra F. Southwell, Julie F. Foley, Brad Bolon, and Susan A. Elmore.
Toxicologic Pathology (2017) DOI: https://doi.org/10.1177/0192623317728134 PMID: 28891434

Publication

Abstract

Evaluation of the central nervous system (CNS) in the developing mouse presents unique challenges, given the complexity of ontogenesis, marked structural reorganization over very short distances in 3 dimensions each hour, and numerous developmental events susceptible to genetic and environmental influences. Developmental defects affecting the brain and spinal cord arise frequently both in utero and perinatally as spontaneous events, following teratogen exposure, and as sequelae to induced mutations and thus are a common factor in embryonic and perinatal lethality in many mouse models. Knowledge of normal organ and cellular architecture and differentiation throughout the mouse's life span is crucial to identify and characterize neurodevelopmental lesions. By providing a well-illustrated overview summarizing major events of normal in utero and perinatal mouse CNS development with examples of common developmental abnormalities, this annotated, color atlas can be used to identify normal structure and histology when phenotyping genetically engineered mice and will enhance efforts to describe and interpret brain and spinal cord malformations as causes of mouse embryonic and perinatal lethal phenotypes. The schematics and images in this atlas illustrate major developmental events during gestation from embryonic day (E)7.5 to E18.5 and after birth from postnatal day (P)1 to P21.

Figures

Figure 1. Key stages and structures of neural tissue histogenesis.

This flow diagram illustrates stages at which select brain structures are derived in forming the developing central nervous system.

Figure 2. Main subdivisions of the embryonic mouse central nervous system.

The early embryonic brain (left image) is composed of 3 swellings at the cephalic end of the neural tube that develop into 3 primary brain vesicles: prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). Soon after (right image), the 3 vesicles shift their contours to assume a 5-vesicle conformation. The prosencephalon divides into the telencephalon (paired cerebral hemispheres) and the diencephalon (thalamus and hypothalamus). The mesencephalon does not subdivide. The rhombencephalon partitions into the metencephalon (cerebellum and pons) and the myelencephalon (medulla oblongata). The caudal end of the neural tube develops into the spinal cord.

Figure 3. Embryonic transformation of the mouse brain from a 3- to a 5-vesicle structure.

(A, C, and E) Structure of the 3-vesicle brain as shown in diagrammatic representation, hematoxylin and eosin (H&E)-stained sagittal section and gross image showing the prosencephalon (PRO), mesencephalon (MS), rhombencephalon (RHO), and spinal cord (SC) in a E9.0 mouse embryo.
(B, D, and F) Structure of the 5-vesicle brain as shown in diagrammatic representation, H&E-stained sagittal section and gross image of an E11.5 mouse embryo. At this later developmental stage, the PRO expands into the telencephalon (T) and the diencephalon (D), the MS remains unchanged, and the RHO becomes the metencephalon (MT) and myelencephalon (MY). The SC is evident in the histologic section as 2 oblique profiles rather than a longitudinal column because the curled axis of the developing mouse embryo imparts a twist on the caudal part of the organ. CNP = caudal neuropore.

Figure 4. Diagrammatic representation of neurulation in the mouse embryo.

Illustrations demonstrating key stages in neurulation represent the intact embryo at 2 early stages of development with representative transverse sections through the embryo. The red dashed lines in A, C, and E indicate the regions for the corresponding cross sections in B, D, and F, respectively. (A and B) Embryo at E7.5. Cephalization begins with the presence of enlarged head folds and formation of the neural plate (NPL) from the ectoderm (ECT). The neural groove (NG) begins to form as a forward extension of the primitive streak (PMS), while the preoptic sulcus (POS) becomes visible as a small depression on the caudal portion of the neural folds. On cross section, the mesoderm (MES) is subjacent to the neuroectoderm (NECT) of the NPL and is confined on the inner surface by the endoderm (END). (C and D) Embryo at E8.0. Convergence of the neural folds (NF) as well as the appearance of the notochord (N) and first few somite pairs (S) occurs in conjunction with the initiation of neural tube formation beginning at closure (fusion site) 1. (E and F) Embryo at E8.5. Neural folds in the cephalic region begin to fuse along 3 specific closure sites (1–3) and progress in a zipper-like fashion in both directions, thus forming a neural tube (NT) that differentiates into the 3-vesicle brain rostrally and the spinal cord caudally. In closing, the neural crest cells (NCRs) at the edges of the neural folds migrate beneath the neuroectoderm and assume a position in the mesodermal layer adjacent to the neural tube. The openings at the ends of the neural tube represent the rostral (RNP) and caudal (CNP) neuropores. (G and H) Embryo at E9.0. Segmental differentiation of the neural tube into the primitive 3 vesicles: prosencephalon (PRO), mesencephalon (MS), and rhombencephalon (RHO). NCRs migrate and differentiate just lateral to the spinal cord (SC), while somites give rise to the dermatome (DER) and myotome (MYO). HRT = heart, OV = optic vesicle.

Figure 5. Representative image of an E9.5 embryonic mouse brain.

Hematoxylin and eosin–stained, transverse section. CN = cranial nerve ganglion (neural crest); FV = fourth ventricle; FVR = fourth ventricle roof; HV = head vein; IFR = infundibular recess; LT = lamina terminalis; M = mesenchyme; OP = olfactory placode; OS = optic stalk; OVE = optic vesicle neuroepithelium; PV = prosencephalic vesicle; RP = Rathke’s pouch; TV= third ventricle.

Figure 6. Representative images of an E12.5 embryonic mouse brain.

Hematoxylin and eosin–stained sagittal (A) and transverse (B) sections. AP = alar plate; CB = cerebellum; CF = choroidal fissure; CHP = choroid plexus; CS = corpus striatum; EM = ectomeninx; FC = falx cerebri; FV = fourth ventricle; FVR = fourth ventricle roof; HT = hypothalamus; IVF = interventricular foramen; LGE = lateral ganglionic eminence; LV = lateral ventricle; M = mesenchyme; MDS = median sulcus; MGE = medial ganglionic eminence; MO = medulla oblongata; MV = mesencephalic vesicle; NC = nasal cavity; NPC = neopallial cortex; O = oropharynx; P = pons; PG = pituitary gland; SC = spinal cord; TC = tentorium cerebelli; TH = thalamus; TO = tongue; TV = third ventricle.

Figure 7. Representative images of the cerebral cortex during brain development.

Hematoxylin and eosin–stained sections of the prosencephalic (A) and telencephalic (B, C, D, E, and F) walls. (A) E9.5, sagittal section. (B) E11.5, transverse section. (C) E13.5, coronal section. (D) E15.5, coronal section. (E) E17.5, coronal section. (F) P21, coronal section. CC = corpus callosum; CP = cortical plate; CTX I-VI = cortical layer I-VI; EP = ependymal layer; H = hippocampus; IZ = intermediate zone; MAR = marginal layer; PP = cortical preplate; SBP = cortical subplate; SZ = subventricular zone; VZ = ventricular zone.

Figure 8. Representative images of the pituitary gland during brain development.

Hematoxylin and eosin–stained, sagittal sections. (A) E11.5. (B) E12.5. (C) E13.5. (D) E18.5. FV = fourth ventricle; IFR = infundibular recess; O = oropharynx; PD = pars distalis (adenohypophysis); PI = pars intermedia; PN = pars nervosa (neurohypophysis); PS = pituitary stalk; RP = Rathke’s pouch; TV = third ventricle. * = Vascular network derived from the plexus of the diencephalic floor.

Figure 9. Representative images of the transient neural lumen occlusion of the spinal cord.

Hematoxylin and eosin–stained, coronal (dorsoventral) sections of an E11.5 embryo. Neural lumen occlusion in the spinal cord of the caudal trunk results in the rise of fluid pressure within the cephalic neural tube and, thus, dilation of the brain vesicles during neurulation. (A) The lumen of the proximal neural tube is narrowed with apposition of opposite sides but complete patency. (B) The lumen of the distal end of the neural tube is segmentally occluded (white arrows). BP = basal plate; CEN = central canal; DRG = dorsal root ganglion; EP = ependymal layer; FP = floor plate; MAN = mantle layer; MAR = marginal layer; RFP = roof plate; S = somite; VR = ventral root.

Figure 10. Representative images of secondary neurulation.

Hematoxylin and eosin–stained, transverse sections of an E12.5 embryo. Secondary neurulation forms the neural tube (NT) caudal to the caudal neuropore through the condensation of tail bud mesenchyme (M), which undergoes mesenchymal-to-epithelial transition to form a medullary plate (MP) of neuroepithelium. (A and B) Caudal tail bud and mid-tail bud, respectively. The MP consists of columnar epithelium from mesenchymal cells that extend dorsoventrally from the surface ectoderm (SE). (C) Cranial tail bud. A slit-like lumen appears below the MP, and the plate begins to round while cavitating to form the neural lumen (NL). The center then connects to the lumen of the remainder of the neural tube. The notochord (N) forms from mesenchymal cells directly ventral to the secondary neural tube. S = somite; TG = tail gut.

Figure 11. Representative images of E11.5 embryonic mouse brain.

Hematoxylin and eosin–stained sections. (A) Sagittal section. (B, C, and D) Transverse sections, superficial (B) to deep (D). A = amnion; DRG = dorsal root ganglion; EP = ependymal layer; FBA = first branchial arch; FV = fourth ventricle; FVR = fourth ventricle roof; HRT = heart; HV = head vein; IFR = infundibular recess; IVF = interventricular foramen; LT = lamina terminalis; M = mesenchyme; MAN = mantle layer; MAR = marginal layer; MV = mesencephalic vesicle; NL = neural lumen of spinal cord; NPC = neopallial cortex; NT = neural tube; OE = optic eminence; PG = pituitary gland; TEV = telencephalic vesicle; TV = third ventricle; VG = cranial nerve V (trigeminal) ganglion.

Figure 12. Representative image of forebrain ganglionic eminences at E12.5.

Hematoxylin and eosin–stained, transverse section, high magnification of ganglionic eminences in Figure 6B. Ganglionic eminences are transitory, embryonic brain structures that protrude into the lateral ventricles (LV) of the ventral telencephalon and guide tangential migration of neural cells. The lateral ganglionic eminence (LGE) gives rise to the striatum (caudate and putamen dorsally, nucleus of accumbens and olfactory tubercle ventrally), and the medial ganglionic eminence (MGE) gives rise to the globus pallidus and contributes to the population of GABAergic (γ-aminobutyric acid-containing) interneurons and oligodendrocytes of the developing cerebral cortex and other telencephalic structures. The caudal eminence (not pictured) differentiates into the amygdaloid body. H = hippocampus; LT = lamina terminalis; TH = thalamus.

Figure 13. Representative image of the developing eye at E11.5.

Hematoxylin and eosin–stained, transverse section. IRS = intraretinal space; LN = lens; M = mesenchyme; NR = neural retina; OR = optic recess; OS = optic stalk; RPE = retinal pigmented epithelium; arrowhead = nucleated red blood cells.

Figure 14. Representative image of several cranial nerve (CN) ganglia and CNs at E11.5.

Hematoxylin and eosin–stained, transverse section. CEN = central canal of the spinal cord; HV = head vein; IXG = cranial nerve IX (glossopharyngeal) ganglion; LT = lamina terminalis; MYF = myencephalon floor; NT = neural tube; OM = occipital myotome; OTV = otic vesicle; TEV = telencephalic vesicle; TV = third ventricle; VG = cranial nerve V (trigeminal) ganglion; VIIG = cranial nerve VII (facial) ganglion; VIIIG = cranial nerve VIII (vestibulocochlear) ganglion; XI = cranial nerve XI (accessory); XIIR = cranial nerve XII (hypoglossal) rootlets.

Figure 15. Representative images of the E13.5 mouse brain.

Hematoxylin and eosin–stained sections. (A and B) Sagittal sections, medial to lateral. (C and D) Transverse sections, superficial to deep. AP = alar plate; BOC = basioccipital bone, cartilage primordium; CB = cerebellum; CDC = caudal commissure; CDP = caudate/putamen; CF = choroidal fissure; CHP = choroid plexus; CS = corpus striatum; DRG = dorsal root ganglion; E = esophagus; ELS = endolymphatic sac; EM = ectomeninx; EP = ependymal layer; FC = falx cerebri; FV = fourth ventricle; H = hippocampus; HT = hypothalamus; HTS = hypothalamic sulcus; IC = internal capsule; IVF = interventricular foramen; LGE = lateral ganglionic eminence; LT = lamina terminalis; LV = lateral ventricle; M = mesenchyme; MAN = mantle layer; MAR = marginal layer; MBR = midbrain roof; MGE = medial ganglionic eminence; MO = medulla oblongata; MV = mesencephalic vesicle; NC = nasal cavity; NPC = neopallial cortex; O = oropharynx; OL = olfactory lobe; P = pons; PG = pituitary gland; PNR = pineal recess; SC = spinal cord; TC = tentorium cerebelli; TH = thalamus; TO = tongue; TV = third ventricle; VC = vertebrae, cartilage primordium.

Figure 16. Representative images of choroid plexus and olfactory nerve in the E12.5 mouse brain.

Hematoxylin and eosin–stained sections. (A) High magnification of the choroid plexus region in Figure 6B. (B) High magnification of Figure 6A, showing olfactory nerve (cranial nerve I) passing from the olfactory neuroepithelium of the nasal cavity toward the olfactory cortex. C = capillary; CPE = choroid plexus epithelial cell; CS = corpus striatum; FV = fourth ventricle; I = cranial nerve I (olfactory); LV = lateral ventricle; NC = nasal cavity; NPC = neopallial cortex; OLE = olfactory epithelium; TV = third ventricle.

Figure 17. Representative images of the embryonic mouse spinal cord.

Hematoxylin and eosin–stained, transverse sections. (A and B) E12.5. The mantle (MAN) and marginal (MAR) zones gradually replace a diminishing ventricular zone (VZ) of the spinal cord. Minimal regional differences in morphology exist among the cervical, thoracic, and lumbar levels of the spinal cord. The white arrowhead denotes a site of luminal occlusion. (C) E15.5. The gray column of the dorsal horn (DH) covers a larger cross-sectional area than the gray column of the ventral horn (VH), while the volume of the white matter increases steadily, especially in the ventral funiculus (VF) and lateral funiculus (LF). The dorsal root ganglia (DRG) are prominent along the entire dorsolateral length of the spinal cord. The central canal (CEN) continues to decrease in diameter. (D) E18.5, cervical spinal cord. (E) E18.5, mid-thoracic spinal cord. (F) E18.5, lumbar spinal cord. AP = alar plate; BP = basal plate; DM = dura mater; DMF = dorsal median fissure; DR = dorsal nerve root; FP = floor plate; LM = leptomeninges; RFP = roof plate; SL = sulcus limitans; VC = vertebrae, cartilage primordium; VR = ventral root; VSA = ventral spinal artery.

Figure 18. Representative images of the embryonic mouse hippocampus during brain development.

Hematoxylin and eosin–stained, coronal sections. (A) E13.5. (B) E15.5. (C) E17.5. (D) P21. CA1-3 = cornu ammonis 1-3; CC = corpus callosum; CG = cingulated cortex; CHP = choroid plexus; DG = dentate gyrus; GL = granular cell layer; HIF = hippocampal fissure; HIL = hilus; LV = lateral ventricle; MAN/IZ = mantle layer/intermediate zone; MCL = molecular cell layer; PO = polymorph layer; SLM = stratum lacunosum-moleculare; SLU = stratum lucidum; SOR = stratum oriens; SPY = stratum pyramidale; SR = stratum radiatum; TEV = telencephalic vesicle; VZ = ventricular zone.

Figure 19. Representative image of the embryonic forebrain at E15.5.

Hematoxylin and eosin–stained, sagittal section. CHP = choroid plexus; CP = cortical plate; CS = corpus striatum; I = cranial nerve I (olfactory) IZ = intermediate zone; LV = lateral ventricle; MZ = marginal zone; NC = nasal cavity; NPC = neopallial cortex; O = oropharynx; OL/OB = olfactory lobe/olfactory bulb; OLE = olfactory epithelium; TBC = turbinate bone, cartilage primordium; VZ = ventricular zone.

Figure 20. Representative image of the embryonic mouse brain at E14.5.

Hematoxylin and eosin–stained, transverse section. AP = alar plate; CBP = cerebellar primordium; CHP = choroid plexus; CS = corpus striatum; ELS = endolymphatic sac; FC = falx cerebri; FV = fourth ventricle; HT = hypothalamus; IC = internal capsule; LV = lateral ventricle; MO = medulla oblongata; MOR = medulla oblongata roof; P = pons; RL = rhombic lip; SAS = subarachnoid space (future); TC = tentorium cerebelli; TH = thalamus; TV = third ventricle.

Figure 21. Representative images of the embryonic mouse cerebellum during brain development.

Hematoxylin and eosin–stained, sagittal sections. (A and B) E15.5, low and high magnifications, respectively. (C and D) E18.5, low and high magnifications, respectively. (E and F) P21, low and high magnifications, respectively. CBC = cerebellar cortex; CB I-X = cerebellar lobe I-X; CBM = cerebellar medulla; CHP = choroid plexus; CL = central lobe; EGL = external granular cell layer; GL = granular cell layer; GT = germinal trigone; IGL = internal granular cell layer; MCL = molecular cell layer; PL = Purkinje cell layer; PM = pia mater; POL = posterior lobe; RBL = rostrobasal lobe; RDL = rostrodorsal lobe; TEC = tectum; VL = ventral lobe; * = primary fissures.

Figure 22. Representative image of the embryonic mouse brain at E15.5.

Hematoxylin and eosin–stained, transverse section. CEN = central canal; DH = dorsal horn; EB = exoccipital bone; EL = eyelid; EOM = extrinsic ocular muscle; I = cranial nerve I (olfactory); IRS = intraretinal space; IXG = cranial nerve IX (glossopharyngeal) ganglion; LN = lens; MO = medulla oblongata; NR = neural retina; OL = olfactory lobe; OLE = olfactory epithelium; PIN = pinna; RP = Rathke’s pouch; SA = saccule/utricle; SC = spinal cord; SCC = semicircular canal; TV = third ventricle; VG = cranial nerve V (trigeminal) ganglion; VH = ventral horn; VII = cranial nerve VII (facial); VIIG = cranial nerve VII (facial) ganglion; VIIIG = cranial nerve VIII (vestibulocochlear) ganglion; XI = cranial nerve XI (accessory).

Figure 23. Representative images of the embryonic mouse brain at E18.5.

Hematoxylin and eosin–stained coronal (A) and sagittal (B) sections. CDP = caudate putamen; CHP = choroid plexus; CP = cortical plate; CS = corpus striatum; DM = dura mater; H = hippocampus; IA = interthalamic adhesion; IC = internal capsule; IZ = intermediate zone; LV = lateral ventricle; MZ = marginal zone; NPC = neopallial cortex; OL/OB = olfactory lobe/olfactory bulb; OLV = olfactory ventricle; PM = pia mater; PNG = pineal gland; RCO = rostral commissure; RON = rostral olfactory nucleus; SAS = subarachnoid space (future); SO = subcommissural organ; TH = thalamus; TV = third ventricle; VZ = ventricular zone.

Figure 24. Representative image of the embryonic mouse brain at E18.5.

Hematoxylin and eosin–stained, sagittal section. CB = cerebellum; CDC = caudal commissure; CHP = choroid plexus; CTX = cortex; FV = fourth ventricle; FVR = fourth ventricle roof; I = cranial nerve I (olfactory); LV = lateral ventricle; LX = larynx; MBR = midbrain roof; MO = medulla oblongata; MV = mesencephalic vesicle (cerebral aqueduct); NC = nasal cavity; NPH = nasopharynx; OL = olfactory lobe; P = pons; PG = pituitary gland; PNG = pineal gland; SC = spinal cord; SP = soft palate; TH = thalamus; TO = tongue; VC= vertebrae, cartilage primordium; * = mesencephalic aqueduct.

Figure 25. Chronology of neuron production in the developing mouse central nervous system.

Neuron production for different brain regions takes place at distinct stages of prenatal and early postnatal life. Some regions (e.g., hippocampus and olfactory bulb) experience 2 neuronogenesis peaks, representing the critical periods for generating unique cell classes. The vertical line on day 20 represents the time of birth. Figure adapted from Rodier (1980) by permission of John Wiley.

Figure 26. Representative image of the rostral migratory stream at P7.

Late appearing olfactory bulb germinal cells originate from the subventricular zone surrounding the rostral margins of the lateral ventricles (LV) and migrate as the “rostral migratory stream” (RMS) along the collapsed remnant of the olfactory ventricle to reach the olfactory bulbs (OB). CTX = cortex; H = hippocampus; TV = third ventricle.

Figure 27. Spectrum of common cephalic axial dysraphic malformations (or neural tube defects [NTDs]) affecting the brain in near-term (E17.5) mouse embryos.

Relative to normal control littermates (N), cranial NTDs form a continuum. Encephalocoele (E) presents as a small protuberance of meninges-covered cerebral cortex on the forehead or crown. Exencephaly (X) exhibits complete exposure of the cerebrum and midbrain. Anencephaly (A) is shown by a complete absence of the brain (± a portion of the brainstem). Holoprosencephaly (H) arises from failure of the primary forebrain vesicle (prosencephalon) to differentiate into paired secondary (telencephalic) vesicles. The latter 3 severe NTDs usually are accompanied by craniofacial defects such as hypoplasia or aplasia of the eyes and jaws (as seen in here for H). In this case, NTDs were induced by maternal inhalation of methanol at 15,000 ppm for 6 hr daily during the period of neural fold formation and neural tube closure (E7–E9). Figure reproduced from Bolon, Welsch, and Morgan (1994) with permission.

Tables

Table 1. Timing of Major Milestones in Nervous System Development.

Table 2. Timing of Major Milestones in Pituitary and Pineal Gland Development.

Table 3. Timing of Major Milestones in Sensory System Development.

Supplemental Materials

Supplemental Material