Genetic patterning of the developing mouse tail at the time of posterior neuropore closure

Neurulation has been suggested to involve both factors intrinsic and extrinsic to the neuroepithelium. In the curly tail (ct) mutant mouse embryo, final closure of the posterior neuropore is delayed to varying extents resulting in neural tube defects. Evidence was presented recently (Brook et al., 1991 Development 113, 671–678) to suggest that enhanced ventral curvature of the caudal region is responsible for the neurulation defect, which probably originates from an abnormally reduced rate of cell proliferation affecting the hindgut endoderm and notochord, but not the neuroepithelium (Copp et al., 1988, Development 104, 285–295). This axial curvature probably generates a mechanical stress on the posterior neuropore, opposing normal closure. We predicted, therefore, that the ct/ct posterior neuropore should be capable of normal closure if the neuropore should be capable of normal closure if the neuroepithelium is isolated from its adjacent tissues. This prediction was tested by in vitro culture of ct/ct posterior neuropore regions, isolated by a cut caudal to the 5th from last somite. In experimental explants, the neuroepithelium of the posterior neuropore, together with the contiguous portion of the neural tube, were separated mechanically from all adjacent non-neural tissues. The posterior neuropore closed in these explants at a similar rate to isolated posterior neuropore regions of non-mutant embryos. By contrast, control ct/ct explants, in which the caudal region was isolated but the neuroepithelium was left attached to adjacent tissues, showed delayed neurulation. To examine further the idea that axial curvature may be a general mechanism regulating neurulation, we cultured chick embryos on curved substrata in vitro. Slight curvature of the body axis (maximally 1 degree per mm axial length), of either concave or convex nature, resulted in delay of posterior neuropore closure in the chick embryo. Both incidence and extent of closure delay correlated with the degree of curvature that was imposed. We propose that during normal embryogenesis the rate of neurulation is related to the angle of axial curvature, such that experimental alterations in curvature will have differing effects (either enhancement or delay of closure) depending on the angle of curvature at which neurulation normally occurs in a given species, or at a given level of the body axis.

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The T gene is necessary for normal mesodermal morphogenetic cell movements during gastrulation

Development ◽

10.1242/dev.121.3.877 ◽

1995 ◽

Vol 121 (3) ◽

pp. 877-886 ◽

Cited By ~ 27

Author(s):

V. Wilson ◽

L. Manson ◽

W.C. Skarnes ◽

R.S. Beddington

Keyword(s):

T Cells ◽

Neural Tube ◽

Es Cells ◽

Embryonic Stem ◽

Primitive Streak ◽

Distal Portion ◽

Adhesion Properties ◽

Cell Clones ◽

Posterior Neuropore ◽

Pass Through

The T (Brachyury) deletion in mouse is responsible for defective primitive streak and notochord morphogenesis, leading to a failure of the axis to elongate properly posterior to the forelimb bud. T/T embryonic stem (ES) cells colonise wild-type embryos, but in chimeras at 10.5 days post coitum (dpc) onwards they are found predominantly in the distal tail, while trunk paraxial and lateral mesoderm are deficient in T/T cells (Wilson, V., Rashbass, P. and Beddington, R. S. P. (1992) Development 117, 1321–1331). To determine the origin of this abnormal tissue distribution, we have isolated T/T and control T/+ ES cell clones which express lacZ constitutively using a gene trap strategy. Visualisation of T/T cell distribution in chimeric embryos throughout gastrulation up to 10.5 dpc shows that a progressive buildup of T/T cells in the primitive streak during gastrulation leads to their incorporation into the tailbud. These observations make it likely that one role of the T gene product is to act during gastrulation to alter cell surface (probably adhesion) properties as cells pass through the primitive streak. As the chimeric tail elongates at 10.5 dpc, abnormal morphology in the most distal portion becomes apparent. Comparison of T expression in the developing tailbud with the sites of accumulation of T/T cells in chimeras shows that T/T cells collect in sites where T would normally be expressed. T expression becomes internalised in the tailbud following posterior neuropore closure while, in abnormal chimeric tails, T/T cells remain on the surface of the distal tail. We conclude that prevention of posterior neuropore closure by the wedge of T/T cells remaining in the primitive streak after gastrulation is one source of the abnormal tail phenotypes observed. Accumulation of T/T cells in the node and anterior streak during gastrulation results in the preferential incorporation of T/T cells into the ventral portion of the neural tube and axial mesoderm. The latter forms compact blocks which are often fused with the ventral neural tube, reminiscent of the notochordal defects seen in intact mutants. Such fusions may be attributed to cell-autonomous changes in cell adhesion, possibly related to those observed at earlier stages in the primitive streak.

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Comparative remarks on the development of the tail cord among higher vertebrates

Development ◽

10.1242/dev.32.2.355 ◽

1974 ◽

Vol 32 (2) ◽

pp. 355-363

Author(s):

A. F. Hughes ◽

R. B. Freeman

Keyword(s):

Neural Tube ◽

Tail Bud ◽

Caudal Region ◽

Posterior Neuropore ◽

Irregular Growth

The development of the caudal region of the neural tube is compared in tailed mammals with that of the chick and human. In rat, mouse, opossum and pig, the lumen of the cord extends caudally in an even manner, whereas in the chick and in man the addition of small cavities to the lumen results in a phase of irregular growth. In mammals with unreduced tails, the site of closure of the posterior neuropore is at the tip of the tail, whereas in pig, man and in the chick closure occurs before the formation of the tail-bud. The teratological implications of these findings are discussed.

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Differential deposition of basement membrane components during formation of the caudal neural tube in the mouse embryo

Development ◽

10.1242/dev.99.4.509 ◽

1987 ◽

Vol 99 (4) ◽

pp. 509-519

Author(s):

K.S. O'Shea

Keyword(s):

Basement Membrane ◽

Type Iv Collagen ◽

Heparan Sulphate ◽

Heparan Sulphate Proteoglycan ◽

Sulphate Proteoglycan ◽

Secondary Neurulation ◽

Type Iv ◽

Posterior Neuropore ◽

Membrane Components ◽

Basement Membrane Components

The distribution of basement membrane and extracellular matrix components laminin, fibronectin, type IV collagen and heparan sulphate proteoglycan was examined during posterior neuropore closure and secondary neurulation in the mouse embryo. During posterior neuropore closure, these components were densely deposited in basement membranes of neuroepithelium, blood vessels, gut and notochord; although deposition was sparse in the midline of the regressing primitive streak. During secondary neurulation, mesenchymal cells formed an initial aggregate near the dorsal surface, which canalized and merged with the anterior neuroepithelium. With aggregation, fibronectin and heparan sulphate proteoglycan were first detected at the base of a 3- to 4-layer zone of radially organized cells. With formation of a lumen within the aggregate, laminin and type IV collagen were also deposited in the forming basement membrane. During both posterior neuropore closure and secondary neurulation, fibronectin and heparan sulphate proteoglycan were associated with the most caudal portion of the neuroepithelium, the region where newly formed epithelium merges with the consolidated neuroepithelium. In regions of neural crest migration, the deposition of basement membrane components was altered, lacking laminin and type IV collagen, with increased deposition of fibronectin and heparan sulphate proteoglycan.

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Genesis and prevention of spinal neural tube defects in the curly tail mutant mouse: involvement of retinoic acid and its nuclear receptors RAR-beta and RAR-gamma

Development ◽

10.1242/dev.121.3.681 ◽

1995 ◽

Vol 121 (3) ◽

pp. 681-691

Author(s):

W.H. Chen ◽

G.M. Morriss-Kay ◽

A.J. Copp

Keyword(s):

Retinoic Acid ◽

Neural Tube ◽

Neural Tube Defects ◽

In Situ Hybridisation ◽

Tail Bud ◽

Retinoic Acid Signalling ◽

All Trans Retinoic Acid ◽

Posterior Neuropore ◽

Computerised Image Analysis ◽

Curly Tail

A role for all-trans-retinoic acid in spinal neurulation is suggested by: (1) the reciprocal domains of expression of the retinoic acid receptors RAR-beta and RAR-gamma in the region of the closed neural tube and open posterior neuropore, respectively, and (2) the preventive effect of maternally administered retinoic acid (5 mg/kg) on spinal neural tube defects in curly tail (ct/ct) mice. Using in situ hybridisation and computerised image analysis we show here that in ct/ct embryos, RAR-beta transcripts are deficient in the hindgut endoderm, a tissue whose proliferation rate is abnormal in the ct mutant, and RAR-gamma transcripts are deficient in the tail bud and posterior neuropore region. The degree of deficiency of RAR-gamma transcripts is correlated with the severity of delay of posterior neuropore closure. As early as 2 hours following RA treatment at 10 days 8 hours post coitum, i.e. well before any morphogenetic effects are detectable, RAR-beta expression is specifically upregulated in the hindgut endoderm, and the abnormal expression pattern of RAR-gamma is also altered. These results suggest that the spinal neural tube defects which characterise the curly tail phenotype may be due to interaction between the ct gene product and one or more aspects of the retinoic acid signalling pathway.

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Neural tube development in mutant (curly tail) and normal mouse embryos: the timing of posterior neuropore closure in vivo and in vitro

Development ◽

10.1242/dev.69.1.151 ◽

1982 ◽

Vol 69 (1) ◽

pp. 151-167

Author(s):

A. J. Copp ◽

M. J. Seller ◽

P. E. Polani

Keyword(s):

Neural Tube ◽

Neural Tube Defects ◽

Mouse Embryos ◽

Injection Technique ◽

Posterior Neuropore ◽

Curly Tail ◽

Mechanisms Of Development ◽

Delayed Closure

A dye-injection technique has been used to determine the developmental stage at which posterior neuropore (PNP) closure occurs in normal and mutant curly tail mouse embryos. In vivo, the majority of non-mutant embryos undergo PNP closure between 30 and 34 somites whereas approximately 50% of all mutant embryos show delayed closure, and around 20% maintain an open PNP even at advanced stages of development. A similar result has been found for embryos developing in vitro from the headfold stage. Later in development, 50–60% of mutant embryos in vivo develop tail flexion defects, and 15–20% lumbosacral myeloschisis. This supports the view that delayed PNP closure is the main developmental lesion leading to the appearance of caudal neural tube defects in curly tail mice. The neural tube is closed in the region of tail flexion defects, but it is locally overexpanded and abnormal in position. The significance of these observations is discussed in relation to possible mechanisms of development of lumbosacral and caudal neural tube defects. This paper constitutes the first demonstration of the development of a genetically induced malformation in vitro.

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Accumulation of basement membrane-associated hyaluronate is reduced in the posterior neuropore region of mutant (curly tail) mouse embryos developing spinal neural tube defects

Developmental Biology ◽

10.1016/0012-1606(88)90353-3 ◽

1988 ◽

Vol 130 (2) ◽

pp. 583-590 ◽

Cited By ~ 41

Author(s):

Andrew J. Copp ◽

Merton Bernfield

Keyword(s):

Basement Membrane ◽

Neural Tube ◽

Neural Tube Defects ◽

Mouse Embryos ◽

Posterior Neuropore ◽

Curly Tail

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Retinoic acid-induced spina bifida: evidence for a pathogenetic mechanism

Development ◽

10.1242/dev.108.1.73 ◽

1990 ◽

Vol 108 (1) ◽

pp. 73-81 ◽

Cited By ~ 4

Author(s):

A.J. Alles ◽

K.K. Sulik

Keyword(s):

Cell Death ◽

Retinoic Acid ◽

Spina Bifida ◽

Nile Blue ◽

Vital Staining ◽

Primitive Streak ◽

Histological Techniques ◽

Stage Of Development ◽

Spina Bifida Aperta ◽

Posterior Neuropore

Treatment of C57Bl/6J mice with three successive doses of all-trans retinoic acid (28 mg kg-1 body weight) on 8 day, 6 h (8d,6h), 8d,12h, and 8d,18h of gestation resulted in a high incidence (79%, 31/39 fetuses) of spina bifida with myeloschisis (spina bifida aperta) in near term fetuses. Twelve hours following the last maternal dose (9d,6h), the caudal aspects of treated embryos, were abnormal, with eversion of the neural plate at the posterior neuropore, as compared to its normal concavity in comparably staged control specimens. This eversion persisted in affected embryos through the time that the posterior neuropore should normally close. The distribution of cell death in control and experimental embryos was determined using vital staining with Nile blue sulphate and with routine histological techniques. Twelve hours following the maternal dosing regimen, experimental embryos showed evidence of excessive cell death, predominantly in the mesenchyme associated with the primitive streak and in the endoderm of the tail gut, both of which are readily identifiable sites of physiological cell death at this stage of development. In addition, the presumptive trunk neural crest cells located in the dorsal midline, cranial to the posterior neuropore, exhibited a marked amount of cell death in the experimental embryos. We propose that the major factor in the generation of spina bifida in this model is excessive cell death in the tail gut and mesenchyme ventral to the neuroepithelium of the posterior neuropore.(ABSTRACT TRUNCATED AT 250 WORDS)

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Closure of Posterior Neuropore; Hind Limb Bud and Tail Bud

The House Mouse ◽

10.1007/978-3-642-88418-4_19 ◽

1989 ◽

pp. 60-65 ◽

Cited By ~ 1

Author(s):

Karl Theiler

Keyword(s):

Hind Limb ◽

Limb Bud ◽

Tail Bud ◽

Posterior Neuropore

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A cell-type-specific abnormality of cell proliferation in mutant (curly tail) mouse embryos developing spinal neural tube defects

Development ◽

10.1242/dev.104.2.285 ◽

1988 ◽

Vol 104 (2) ◽

pp. 285-295 ◽

Cited By ~ 7

Author(s):

A.J. Copp ◽

F.A. Brook ◽

H.J. Roberts

Keyword(s):

Cell Proliferation ◽

Neural Tube ◽

Neural Tube Defects ◽

Posterior Neuropore ◽

Curly Tail ◽

A Cell ◽

Notochord Cells ◽

Cell Type Specific ◽

Reduced Rate ◽

Gut Endoderm

The mouse mutant curly tail (ct) provides a model system for studies of neurulation mechanisms. 60% of ct/ct embryos develop spinal neural tube defects (NTD) as a result of delayed neurulation at the posterior neuropore whereas the remaining 40% of embryos develop normally. In order to investigate the role of cell proliferation during mouse neurulation, cell cycle parameters were studied in curly tail embryos developing spinal NTD and in their normally developing litter-mates. Measurements were made of mitotic index, median length of S-phase and percent reduction of labelling index during a [3H]thymidine pulse-chase experiment. These independent measures of cell proliferation rate indicate a reduced rate of proliferation of gut endoderm and notochord cells in the neuropore region of embryos developing spinal NTD compared with normally developing controls. The incidence of cell death and the relative frequency of mitotic spindle orientations does not differ consistently between normal and abnormal embryos. These results suggest a mechanism of spinal NTD pathogenesis in curly tail embryos based on failure of normal cell proliferation in gut endoderm and notochord.

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