NTR: trigeminal placode

[cmungall]

Related to obophenotype/uberon#693

Should EMAPA have a trigeminal placode? It has other placodes.

On a related note:

[Term]
id: EMAPA:16663
name: trigeminal V preganglion
namespace: anatomical_structure
comment: order=10 for EMAPA:16659.
synonym: "trigeminal preganglion" RELATED []
relationship: ends_at TS15 ! TS15
relationship: part_of EMAPA:36064 ! cranial preganglion
relationship: starts_at TS15 ! TS15

Is the preganglion terminology quite EMAPA specific? Often pregangionic and postganglionic are spatial qualifiers rather than temporal, so there is possibility for confusion here (or this may just be me).

[tfhayamizu]

It appears to me that that the spatial use of pre- and post-ganglionic is usually with regards to nerves.

The EMAPA use of "pre-ganglion" has to do with chronological development, and it is based on the Tissue Indexes that were developed for Matt Kaufman's "The Atlas of Mouse Development" -- presented by Kaufman and Jonathan Bard in "The Anatomical Basis of Mouse Development".

5.3 Tissues present in each stage of mouse development
(Tissues appearing for the first time are shown in UPPERCASE.)

Stage 12 – day 8 (unturned, headfold stage) (p. 225)
neural crest (head)
TRIGEMINAL (V)

Stage 13 – day 8.5 (turning) (p. 225-226)
neural crest (head)
trigeminal (V)
FACIAL-ACOUSTIC (VII-VIII)

Stage 14 – day 9 (p. 226)
neural crest
trigeminal (V) + PRE-GANGLION
facio-acoustic (VII-VIII) and PRE-GANGLION COMPLEX

Stage 15 – day 9.5 (p. 226-227)
neural crest
trigeminal (V) pre-gangion
facial-acoustic (VII-VIII) preganglion complex
GLOSSOPHARYNGEAL-VABUS (IX-X) PREGANGLION COMPLEX (early stage)
GLOSSOPHARYNGEAL (IX) PREGANGLION (late stage)
VAGUS (X) PREGANGLION (late stage)

Stage 16 – day 10 (p. 227-228)
TRIGEMINAL (V) GANGLION (semilunar, Gasserian)
FACIAL-ACOUSTIC (VII-VIII) GANGLION COMPLEX
GLOSSOPHARYNGEAL (IX0 GANGLION (late stage)
VAGUS (X) GANGLION

Accordingly, this correlates with the another Index in the same book

5.4 Index of first occurences of tissues

neural crest (p. 257)
    trigeminal (V) – TS12
    facio-acoustic (VII-VIII) – TS13 (early)
    glossopharyngeal (IX) – TS15
    glossopharyngeal-vagal (IX-X) – TS15
    vagal (X) – TS15

cranial ganglia
    trigeminal (V) semilunar, Gasserian) preganglion – TS14
    trigeminal (V) (semilanar, Gasserian) ganglion – TS16
    facial-acoustic (VII-VIII) pre-ganglion complex – TS14
    facial-acoustic (VII-VIII) ganglion complex – TS16
    acoustic (VIII) future vesticulo-cochlear) – TS16
    vestibulo-cochlear (VIII) – TS20
    vestibulo-cochlear (VIII) – TS20
    cochlear (VIII) – TS20 (late)
    glossopharyngeal-vagal preganglion (IX-X) – TS15 (early stage)
    glossopharyngeal (IX) preganglion – TS15 (late)
    glossopharyngeal (IX) – inferior (petrosal) – TS18 (late)
    glossopharyngeal (IX) – superior – TS18 (late)
    vagus (X) preganglion – TS15 (late)
    vagus (X) ganglion – TS16
    vagus (X) – inferior (nodose) – TS18 
    vagus (X) – superior – TS18

[tfhayamizu]

With regards to "trigeminal placode," the answer is most likely yes for the mouse -- certainly it is reported in mouse literature -- but I will need to investigate further, especially in terms of stage range of occurrence. Interestingly, according to Stark et al. (1997) "Unlike most placodes, the trigeminal placode is not mor- phologically distinct from the surrounding ectoderm. As a consequence, most information about its development comes from observations of placode cells during their migration and gangliogenesis." For the mouse, this study reports "... a strong Pax-3 expression domain in the ectoderm adjacent to the midbrain neural folds (Fig. 7A,B) in a region reminiscent of the chick trigeminal placode." This is quite an old paper and mostly on chick, so I expect there has been more work on this since. I will investigate.