Theiler Staging Criteria for Mouse Embryo Development

TS 1

TS 7(4.5-6)

TS 8(5-6.5)

TS 10(6.5-7.75)

TS 11(7.25-8)

TS 13(8-9.25)

TS 14(8.5-9.75)

TS 15(9-10.25)

TS 16(9.5-10.75)

TS 17(10-11.25)

TS 18(10.5-11.25)

TS 19(11-12.25)

TS 20(11.5-13)

TS 21(12.5-14)

TS 22(13.5-15) TS 23 TS 24 TS 25 TS 26

TS 27

TS 9(6.25-7.25)

For full descriptions of Theiler Staging and mouse anatomy visit http://www.emouseatlas.org/emap/ema/home.html

First sign of radial asymmetry. a Pre-streak (PS), advanced endometrial reaction, ectoplacen-tal cone invaded by blood, extraembryonic ectoderm, embryonic axis visible. b Early streak (ES), gastrulation starts, first evidence of mesoderm.

Implantation and formation of egg cylinder. Ectoplacental cone appears, enlarged epiblast, primary en-doderm lines mural trophectoderm

Differentiation of egg cylinder. Implantation sites 2x3mm.Ectoplacental cone region invaded by maternal blood, Reichertís mem-brane and proamni-otic cavity form

Formation & closure of anterior

neuropore, otic pit indented but not

closed, 3rd branchial arch visible

13-20 somites.Absent: forelimb bud

a Mid streak (MS), amni-otic fold starts to form.

b Late streak, no bud (LSOB), exocoelom.

c Late streak, early bud (LSEB), allantoic bud first

appears, node, amnion closing

Formation of posterior neuro-pore, forelimb bud, forebrain vesicle subdivides21-29 somites.Absent: hindlimb bud, Rathke’s pouch

Posterior neu-ropore closes, formation of hindlimb & tail buds, lens plate, Rathke’s pouch; the indented nasal processes start to form30-34 somites.Absent: thin & long tail

Fingers & toes separate, hair follicles also in cephalic region but not at periphery of vibrissae, eyelids open. Absent: nail pri-mordia, fingers 2-5 parallel

Repositioning of umbilical hernia, eyelids closing, fin-gers 2-5 are parallel, nail primordia visible on toes.Absent: wrinkled skin, fingers & toes joined together

Skin wrinkled, eye-lidsclosed, umbilical hernia is gone. Absent: ear extend-ing over auditory me-atus, long whiskers

Long whiskers, eyes barely visible through closed eyelids, ear covers audi-tory meatus

Newborn mouse Deep lens inden-tation, advanced development of brain tube, tail elongates and thins, umbilical her-nia starts to form35-39 somites.Absent: nasal pits

Closure of lens vesicle, nasal pits, cervical somites no longer visible40-44 somites.Absent: auditory hillocks, anterior footplate

Lens vesicle com-pletely separated from the surface epithelium. Ante-rior, but no posterior, footplate. Auditory hillocks first visible45-47 somites.Absent: retinal pigmentation and sign of fingers

Earliest sign of fingers (splayed-out), posterior footplate apparent, retina pigmentation apparent, tongue well-defined, brain vesicles clear48-51 somites.Absent: 5 rows of whiskers, indented anterior footplate

Fingers separate dis-tally, only indentations between digits of the posterior footplate, long bones of limbs present, hair follicles in pectoral, pelvic and trunk region56-~60 somites.Absent: open eyelids, hair follicles in cephalic region

Anterior footplate indented, elbow and wrist identifiable, 5 rows of whiskers, umbilical hernia now clearly apparent52-55 somites.Absent: hair follicles, fingers separate distally

a Neural plate (NP), head process developing, amnion

completeb Late neural plate (LNP),

elongated allantoic budc Early head fold (EHF)d Late head fold (LHF),

foregut invagination

First appearance of somites.1-4 somites, al-lantois extends, 1st branchial arch, heart starts to form, fore-gut pocket visible, preotic sulcus (at 2-3 somite stage).5-7 somites, allan-tois contacts chorion at the end of TS12Absent: 2nd arch, >7 somites

Turning of the embryo, 1st branchial arch has maxillary and mandibular components, 2nd arch present8-12 somites.Absent: 3rd bran-chial arch

One-cell egg Dividing egg 2-4 cells

Morula 4-16 cells

Blastocyst, inner cell mass apparent16-40 cells

Blastocyst (zona-free) Attachment of blastocyst. Pri-mary endoderm covers blasto-coelic surface of inner cell mass

11

21

32

43

54

64.5

75

86

96.5

107

117.5

128

138.5

149

159.5

1610

1710.5

1811

1911.5

2012

2113

2214

2315

2416

2517

2618

2719

Theiler Stagedpc

TS 12(7.5-8.75)

TS 2(1-2.5)

aaa

bbb

cc

d

TS 5(3-5.5)

TS 3(1-3.5)

TS 4(2-4)

TS 1(0-2.5)

TS 6(4-5.5)

Figures represent development of F1 hybrid (C57BL x CBA) mice. Descriptions of embryos at Theiler Stages (TS) 9 – 11 based on Downs & Davies, 1993, and apply to outbred mice of the PO strain. Numbers in parentheses under Theiler stages represent approximate dpc range. Relative sizes of illustrations not to scale. The cartoons are intended as an illustrative guide only.