nkx3.2 mutant zebrafish accommodate jaw joint loss through a phenocopy of the head shapes of Paleozoic jawless fish

The vertebrate jaw is a versatile feeding apparatus that facilitated explosive diversification. To function, it requires a joint between the upper and lower jaws, so jaw joint defects - such as osteoarthritis or even ankylosis - are often highly disruptive and difficult to study. To describe consequences of jaw-joint dysfunction, we engineered two independent null alleles of a single jaw-joint marker gene, nkx3.2, in zebrafish. These mutations caused zebrafish to become functionally jawless via fusion of the upper and lower jaw cartilages (ankylosis). Despite lacking jaw joints, nkx3.2 mutants survive to adulthood and accommodate this defect by: a) remodeling their skulls; and b) altering their behavior from suction feeding to ram feeding. As a result of remodeling, nkx3.2 mutants developed superficial similarities to the skull shapes observed in two lineages of ancient jawless vertebrates (anaspids and furcacaudiid thelodonts), including: a fixed open gape, reduced snout, and enlarged branchial region. However, no homology exists in individual skull elements between these taxa, and most of the modified elements in the mutant zebrafish occur outside known expression domains of nkx3.2. Therefore, we interpret the adult nkx3.2 phenotype not as a reversal to an ancestral state, but as convergence due to similar functional requirement of feeding without moveable jaws. This remarkable convergence strongly suggests that jaw movements themselves dramatically influence the development of jawed vertebrate skulls, which implies that functionally viable skull morphologies are finite, with or without functional jaws. Because nkx3.2 null zebrafish display prominent joint ankylosis, drastically modified skull shape, and altered feeding behaviors, these mutants provide a unique model with which to investigate mechanisms of skeletal remodeling and joint diseases.

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Mammalian development does not recapitulate suspected key transformations in the evolution of the mammalian middle ear

10.1101/023820 ◽

2015 ◽

Author(s):

Héctor Ramirez-Chaves ◽

Stephen Wroe ◽

Lynne Selwood ◽

Lyn Hinds ◽

Chris Leigh ◽

...

Keyword(s):

Middle Ear ◽

Mammalian Development ◽

Positional Change ◽

Lower Jaw ◽

Dental Eruption ◽

Mesozoic Mammals ◽

Differential Positioning ◽

Jaw Joint ◽

Early Mammalian Development ◽

Land Vertebrates

The tympanic ring, malleus and incus of the mammalian middle ear (MME) derive from the ancestral primary jaw joint of land vertebrates. In Mesozoic mammals, evolutionary detachment of the MME from the lower jaw occurred when Meckel’s cartilage - the last connection between MME and dentary – disappeared. This disappearance is famously recapitulated in early mammalian development. Further developmental recapitulation of Mesozoic MME detachment is thought to occur in the form of negative allometry and posterior/medial replacement of MME bones relative to the jaw joint. However, despite being widely accepted, such detailed recapitulation scenarios have never been quantified. Here we show, based on µCT scans of developmental series of several marsupials and monotremes, that negative allometry of MME bones relative to the skull occurs only after MME detachment, ruling it out as a developmental detachment trigger; additionally, there is no positional change of ectotympanic or malleus relative to the dentary. Differential positioning of MME bones in the two monotreme species is also not developmentally recapitulated. Our results challenge the developmental prerequisites of widely accepted evolutionary scenarios regarding MME detachment. Rather, we observe an association of MME detachment and dental eruption, suggesting a detachment trigger relating to the onset of dentary function.

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Morphometric characteristics and correlation relationships of bone structures of TMJ-jaw joint in extending concepts of individually typological variability

Medical alphabet ◽

10.33667/2078-5631-2019-3-23(398)-44-50 ◽

2019 ◽

Vol 3 (23) ◽

pp. 44-50 ◽

Cited By ~ 4

Author(s):

B. N. Davydov ◽

V. V. Konnov ◽

D. A. Domenyuk ◽

S. О. Ivanyuta ◽

F. V. Samedov ◽

...

Keyword(s):

Temporomandibular Joint ◽

Structural Characteristics ◽

Morphometric Characteristics ◽

Lower Jaw ◽

Mandibular Fossa ◽

Jaw Joint ◽

Bone Structures

The structural characteristics of the morphometric characteristics of the bones of the temporomandibular joint were studied on 103 passported sculls of adults, and the patterns of individual typological variability determining the type of its structure were also determined. According to the results of the study, the main dimensional characteristics of the mandibular fossa, articular tubercle and head of the lower jaw were established. Depending on the ratios of the selected parameters, three forms of the head of the lower jaw, seven forms of the mandibular fossa and seven forms of the articular tubercles are distinguished. Of the presented forms, the most common are the medium-wide head of the lower jaw, the medium-deep medium-wide mandibular fossa and the medium-high medium-wide articular tubercle. The results of the study can be claimed by dentist’s orthopedists and orthodontists when planning the treatment of patients with dentoalveolar anomalies and deformities, as well as patients with full adentia.

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nkx3.2 mutant zebrafish accommodate jaw joint loss through a phenocopy of the head shapes of Paleozoic jawless fish

Journal of Experimental Biology ◽

10.1242/jeb.216945 ◽

2020 ◽

Vol 223 (15) ◽

pp. jeb216945 ◽

Cited By ~ 2

Author(s):

Tetsuto Miyashita ◽

Pranidhi Baddam ◽

Joanna Smeeton ◽

A. Phil Oel ◽

Natasha Natarajan ◽

...

Keyword(s):

Jaw Joint ◽

Jawless Fish

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Individual Muscles Attachments, Action, & Structure

Animal Anatomy for Artists ◽

10.1093/oso/9780195142143.003.0010 ◽

2004 ◽

Author(s):

Eliot Goldfinger

Keyword(s):

Upper Eyelid ◽

Orbicularis Oculi ◽

Facial Muscles ◽

Outer Portion ◽

Lower Jaw ◽

Direct Form ◽

The Face ◽

Jaw Joint ◽

Action Taking ◽

Action Structure

The muscles of the head consist of the chewing muscles (temporalis, masseter, and digastric) and the facial muscles (zygomaticus, orbicularis oris, etc.). The chewing muscles are thick and volumetric, and they originate and insert on bone. They open and close the lower jaw, with the action taking place at the jaw joint (temporomandibular joint). The facial muscles are thin. They originate either from the skull or from the surface of other muscles, and they generally insert into other facial muscles or into the skin. When they contract, they move the features of the face (eyes, nose, mouth, ears). As they pull the facial features, they often gather the skin into folds and wrinkles that lie perpendicular to the direction of their muscular fibers (perpendicular to the direction of pull). The mouth region receives the most muscles; therefore, it is the most mobile part of the face. Some facial muscles are so thin that they do not create any direct form on the surface (caninus, malaris, orbicularis oculi), whereas other facial muscles or their tendons may create surface form directly (buccinator, levator labii maxillaris, zygomaticus, and depressor labii mandibularis). Facial muscles are generally more visible on the surface in the horse and the ox than in the dog and feline. The facial muscles, as they move the eyes, nose, mouth, and ears, generate whatever facial expressions animals are capable of producing. . . . • Attachment: A short ligament at the inner corner of the eye, whose inner end attaches to the skull. . . . . . . • Action: Eyelid portion: closes eyelids (blinking), primarily by depressing the upper eyelid. Outer portion: tightens and compresses the skin surrounding the eye, protecting the eyeball. . . . . . . • Structure: The orbicularis oculi is a flat, elliptical muscle consisting of two portions. The eyelid portion lies in the upper and lower eyelids, and the outer portion surrounds the eye and lies on the skull. . . .

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Radiation Diagnostics in Treatment of Displacement of a Joint Disk of a Temp-Jaw Joint and Myofascial Disorders

Medical Radiology and radiation safety ◽

10.12737/1024-6177-2021-66-3-29-34 ◽

2021 ◽

Vol 66 (3) ◽

pp. 29-34

Author(s):

A. Ilyin ◽

T. Fazylova ◽

A. Dergilev ◽

A. Sudarkina ◽

E. Olesov ◽

...

Keyword(s):

Botulinum Toxin ◽

Temporomandibular Joint ◽

Myofascial Pain ◽

Masticatory Muscles ◽

Articular Disc ◽

Clinical Criteria ◽

Lower Jaw ◽

Treatment Measures ◽

Jaw Joint ◽

Pterygoid Muscles

Purpose: Determination of the volume and sequence of radiation studies in the treatment of patients with displacement of the articular disc of the temporomandibular joint (TMJ)and myofascial pain disorders. Material and methods: The study included 48 patients with displacement of the articular disc of the TMJ and myofascial pain disorders. Clinical criteria for articular displacement were confirmed by MRI and CBCT. Studies of the function of the masticatory muscles were carried out at the Synapsis electromyograph. All patients underwent complex treatment, including relaxation of the masticatory muscles and relief of pain using injections of botulinum toxin in the actual masticatory, temporal and lateral pterygoid muscles (LPM), followed by repositioning split therapy. For the introduction of muscle relaxant in LPM, we have developed and applied external periarticular injection access to LPM. The method is based on reaching the zone of joint attachment of the upper and lower heads of the LPM with MRI navigation. Surveillance continued for up to 12 months with MRI monitoring of the position of the articular disc. Results: The stages of treatment of SJS of the TMJ with control use of MRI and CT, as well as a method for the administration of botulinum toxin under MRI navigation, have been developed. The first stage included CT and MRI of the temporomandibular joint, the second stage – injections of botulinum toxin into the masticatory muscles using the developed periarticular access to the LPM with MRI navigation, as well as CBCT with a splint to control the new (established) position of the lower jaw; the third and fourth stages included continuation of the reduction splint therapy, correction of the splint, observation for 3-6 months with control CBCT after 6 months to assess the position of the mandible without splint. Achieved an increase in the posterior and upper temporomandibular joint distances and the correct position of the lower jaw. Conclusion: Performing radiation studies on time at certain stages of treatment, differing in their content and volume, provided a complete diagnosis, planning treatment measures and monitoring the results.

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Transient role of the middle ear as a lower jaw support across mammals

eLife ◽

10.7554/elife.57860 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 3

Author(s):

Neal Anthwal ◽

Jane C Fenelon ◽

Stephen D Johnston ◽

Marilyn B Renfree ◽

Abigail S Tucker

Keyword(s):

Middle Ear ◽

Cranial Base ◽

The Novel ◽

Vital Function ◽

Lower Jaw ◽

Jaw Joint ◽

Evolution Of Mammals ◽

Joint Form ◽

Insight Into

Mammals articulate their jaws using a novel joint between the dentary and squamosal bones. In eutherian mammals, this joint forms in the embryo, supporting feeding and vocalisation from birth. In contrast, marsupials and monotremes exhibit extreme altriciality and are born before the bones of the novel mammalian jaw joint form. These mammals need to rely on other mechanisms to allow them to feed. Here, we show that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation. The nature of this articulation varies between monotremes and marsupials, with juvenile monotremes retaining a double articulation, similar to that of the fossil mammaliaform Morganucodon, while marsupials use a versican-rich matrix to stabilise the jaw against the cranial base. These findings provide novel insight into the evolution of mammals and the changing relationship between the jaw and ear.

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SINAPS: Prediction of microbial traits from marker gene sequences

10.1101/124156 ◽

2017 ◽

Cited By ~ 4

Author(s):

Robert C. Edgar

Keyword(s):

Ribosomal Rna ◽

Copy Number ◽

Marker Gene ◽

Marker Genes ◽

Positive Staining ◽

Ancestral State ◽

Gene Sequences ◽

State Reconstruction ◽

True Value ◽

Prediction Confidence

AbstractMicrobial communities are often studied by sequencing marker genes such as 16S ribosomal RNA. Marker gene sequences can be used to assess diversity and taxonomy, but do not directly measure functions arising from other genes in the community metagenome. Such functions can be predicted by algorithms that associate marker genes with experimentally determined traits in well-studied species. Typically, such methods use ancestral state reconstruction. Here I describe SINAPS, a new algorithm that predicts traits for marker gene sequences using a fast, simple word-counting algorithm that does not require alignments or trees. A measure of prediction confidence is obtained by bootstrapping. I tested SINAPS predictions from 16S V4 query sequences for traits including energy metabolism, Gram-positive staining, presence of a flagellum, V4 primer mismatches, and 16S copy number. Accuracy was >90% except for copy number, where a large majority of predictions were within +/−2 of the true value.

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