The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The literature retrieved here unambiguously supports that Drosophila melanogaster jaguar (jar) encodes myosin VI (class VI unconventional myosin; previously “95F myosin”), an actin-based motor that is unusual in moving toward the minus/pointed end of actin filaments. (morrison2008geneticcharacterizationof pages 1-2, kisiel2011myosinvicontributes pages 1-2, rogat2002arolefor pages 1-2)
Multiple independent studies explicitly equate the gene name jaguar (jar) with Drosophila myosin VI, including neuronal/synaptic work and spermatogenesis work. (kisiel2011myosinvicontributes pages 1-2, kisiel2014localizationandmobility pages 1-2, noguchi2006myosinvistabilizes pages 1-2)
Working definition (current understanding from these sources): jar encodes a mechanochemical ATPase that converts ATP hydrolysis into movement and/or tension on F-actin, with context-dependent roles either as (i) a motor/transporter or (ii) a tether/anchor that binds actin strongly for extended periods and stabilizes actin-linked structures or vesicle positioning. (kisiel2011myosinvicontributes pages 1-2, noguchi2006myosinvistabilizes pages 1-2, morrison2008geneticcharacterizationof pages 1-2)
As a myosin, jar/myosin VI is an ATP-dependent actin motor: it uses ATP hydrolysis to generate force and movement along actin filaments. (kisiel2014localizationandmobility pages 1-2, rogat2002arolefor pages 1-2)
Myosin VI is described as unique among myosins in moving toward the minus/pointed ends of actin filaments. (kisiel2011myosinvicontributes pages 1-2, morrison2008geneticcharacterizationof pages 1-2, rogat2002arolefor pages 1-2)
Mechanistic features highlighted in Drosophila myosin VI include specialized inserts affecting lever-arm geometry and nucleotide kinetics, consistent with long actin association and dual motor/anchor behavior: an insert between the converter and IQ motif implicated in reversing directionality, and an insert near the nucleotide-binding pocket that restricts ATP access, slows ADP release, and increases actin association time. (kisiel2011myosinvicontributes pages 1-2)
Functional dissection in spermatids shows that both the head (motor) domain and the globular tail (cargo-binding) domain are required for myosin VI localization to actin-cone fronts and for correct actin meshwork formation; conserved partner-binding sites in the globular tail are important for function. (isaji2011myosinviregulates pages 1-2)
In vivo, myosin VI is also repeatedly linked to membrane traffic and actin remodeling, consistent with tail-mediated recruitment to vesicles/complexes and head-mediated force/tethering on F-actin. (rogat2002arolefor pages 1-2, noguchi2006myosinvistabilizes pages 1-2)
The most experimentally grounded “primary functions” emerging from the retrieved Drosophila literature are:
In Drosophila spermatid individualization, myosin VI localizes to the fronts of actin cones and is required to stabilize/promote a branched F-actin meshwork at the cone front. Mutants show cones that fail to accumulate sufficient F-actin during movement, while overexpression enlarges cones and increases F-actin content. (noguchi2006myosinvistabilizes pages 1-2)
The same work provides strong mechanistic evidence for an anchor/tether role: FRAP of GFP-myosin VI indicates myosin VI can remain actin-bound for minutes, suggesting stable binding rather than rapid transport. (noguchi2006myosinvistabilizes pages 1-2)
A complementary spermatogenesis study demonstrates that myosin VI colocalizes with and is required for accumulation of cortactin and Arp2/3 complex on actin structures mediating membrane remodeling, and shows genetic interactions with dynamin, supporting a model in which myosin VI helps couple actin assembly dynamics to membrane remodeling sites. (rogat2002arolefor pages 1-2)
Domain/surface-function mapping further supports that tail partner-binding sites regulate actin-structure specialization (likely by controlling actin assembly regulators), and that localization and actin-organization functions can be partially separable. (isaji2011myosinviregulates pages 1-2)
At the larval neuromuscular junction (NMJ), jar/myosin VI is implicated in maintaining proper synaptic physiology and morphology and is proposed to act as a tether that maintains synaptic vesicles near the bouton periphery. Loss-of-function jar alleles produce locomotor defects, reduced NMJ size metrics, and altered vesicle localization and synaptic transmission properties. (kisiel2011myosinvicontributes pages 1-2)
Direct imaging approaches reinforce this tethering model: FM-dye labeling and FRAP of synaptotagmin-GFP indicate that in jar mutants, newly endocytosed vesicles become distributed throughout boutons rather than peripherally, and vesicles show increased apparent mobility (rapid FRAP recovery), consistent with myosin VI restricting vesicle mobility. (kisiel2014localizationandmobility pages 1-2)
In embryonic neuroblasts, myosin VI/Jar is required for basal localization of the fate determinant adaptor Miranda and for correct spindle orientation. Miranda-containing complexes co-immunoprecipitate Jar and myosin II (Zipper), and Jar binds Miranda directly (GST pull-down). (petritsch2003thedrosophilamyosin pages 1-2)
Quantitatively, in jar322 zygotic null embryos, 30% of metaphase neuroblasts showed Miranda mislocalized in cortical/cytoplasmic patches, and 21% of spindles were misoriented by 80–90° (vs 2% in heterozygotes). RNAi-based reduction of Jar yielded ~50% improper Miranda localization and 45% spindle defects, consistent with Jar’s role in basal targeting/spindle alignment. (petritsch2003thedrosophilamyosin pages 2-3)
Jar localization in dividing neuroblasts is reported as dynamic small cytoplasmic particles (sometimes cortical), with partial basal enrichment in a subset of metaphase neuroblasts and partial overlap with Miranda’s distribution, consistent with a motor/positioning role for determinant complexes. (petritsch2003thedrosophilamyosin pages 2-3)
A genetic note clarifies that complete loss of myosin VI is not lethal in Drosophila; earlier reports of jar322 lethality were likely confounded by deletion of a neighboring gene. However, null animals are recovered at a lower than expected Mendelian frequency, implying myosin VI contributes to robust development even if not absolutely essential for viability. (morrison2008geneticcharacterizationof pages 1-2)
Across contexts, jar/myosin VI is most consistently localized to actin-rich structures associated with membrane remodeling and vesicle positioning:
The strongest pathway-level inference supported by the retrieved texts is that jar/myosin VI is repeatedly embedded in modules linking actin dynamics ↔ membrane trafficking:
Within the retrieved corpus, direct 2023–2024 primary literature focused specifically on D. melanogaster jar/myosin VI functional mechanisms was not recovered, suggesting that (at least for this targeted query set) the most definitive mechanistic studies remain the 2002–2014 experimental literature on spermatogenesis, neuroblasts, and synapses. (rogat2002arolefor pages 1-2, petritsch2003thedrosophilamyosin pages 1-2, kisiel2014localizationandmobility pages 1-2)
Therefore, “recent developments” most defensibly stated from the accessible evidence here are:
(Additional 2023–2024 Drosophila cell-biology papers were retrieved in the broader search but did not contain jar-specific mechanistic results usable for functional annotation under the gene-identification constraints. No claims about jar were drawn from those non-jar texts.)
Although jar is a basic research gene rather than a direct therapeutic target in this Drosophila context, the jar/myosin VI system has practical applications as an in vivo mechanistic testbed:
Primary authors interpret jar/myosin VI as having dual mechanistic modes—transporter vs anchor—depending on context, with Drosophila evidence particularly strong for tethering/anchoring in (i) spermatid actin cones (minutes-long actin binding; stabilization of meshwork) and (ii) synaptic boutons (restriction of vesicle mobility). (noguchi2006myosinvistabilizes pages 1-2, kisiel2014localizationandmobility pages 1-2, kisiel2011myosinvicontributes pages 1-2)
The following table summarizes the principal experimentally supported functional claims and where they were demonstrated.
| Claim/Function | Biological context (tissue/process) | Key experimental evidence (assay/method) | Subcellular localization | Quantitative/statistical data if stated | Key citation details (authors, year, journal, DOI/URL) | PaperQA citation ID |
|---|---|---|---|---|---|---|
| Identity verification: jar (jaguar; Mhc95F) encodes Drosophila myosin VI, an unconventional actin-based motor that moves toward the minus/pointed end of actin filaments | General molecular identity; gene/protein annotation in D. melanogaster | Biochemical and genetic characterization summarized in primary studies; loss-of-function and protein detection in flies | Actin-associated motor; broadly expressed, including embryonic and adult tissues | ~140 kDa protein; six isoforms reported from alternative splicing | Morrison & Miller, 2008, Genetics, doi:10.1534/genetics.107.085969, https://doi.org/10.1534/genetics.107.085969; Kisiel et al., 2011, BMC Neurosci., doi:10.1186/1471-2202-12-65, https://doi.org/10.1186/1471-2202-12-65 | (morrison2008geneticcharacterizationof pages 1-2, kisiel2011myosinvicontributes pages 1-2, majumdar2007functionalanalysisofa pages 35-41) |
| Myosin VI can function as both cargo transporter and anchor/tether, consistent with slow kinetics and strong actin binding | General cell biology; mechanistic interpretation across tissues | Biophysical/mechanistic interpretation in reviews and Drosophila experimental contexts; FRAP and mutant phenotypes support tethering roles | Actin filaments; vesicle-associated and cortical sites | Not numerically stated in retrieved excerpts; FRAP indicates actin binding for minutes in spermatid cones | Noguchi et al., 2006, Mol. Biol. Cell, doi:10.1091/mbc.e06-01-0031, https://doi.org/10.1091/mbc.e06-01-0031; Kisiel et al., 2014, PLoS ONE, doi:10.1371/journal.pone.0102988, https://doi.org/10.1371/journal.pone.0102988 | (noguchi2006myosinvistabilizes pages 1-2, kisiel2014localizationandmobility pages 1-2, kisiel2011myosinvicontributes pages 1-2) |
| Required for basal protein targeting during asymmetric neuroblast division; likely transports or positions the Miranda complex | Embryonic neuroblasts; asymmetric cell division | Anti-Miranda immunoprecipitation, mass spectrometry, anti-Jar co-IP, GST pull-down showing direct Jar-Miranda binding; jar null analysis and RNAi | Jar in small cytoplasmic particles, sometimes cortical; partial basal enrichment in metaphase neuroblasts; overlaps partly with Miranda | In jar322 embryos, 30% of metaphase neuroblasts had Miranda mislocalized; 21% of spindles misoriented by 80–90° vs 2% in heterozygotes; in RNAi, improper Miranda localization in ~50% and spindle defects in 45% | Petritsch et al., 2003, Developmental Cell, doi:10.1016/S1534-5807(03)00020-0, https://doi.org/10.1016/S1534-5807(03)00020-0 | (petritsch2003thedrosophilamyosin pages 2-3, petritsch2003thedrosophilamyosin pages 1-2) |
| Contributes to correct spindle orientation in mitotic neuroblasts, acting downstream of or parallel to apical polarity machinery | Embryonic neuroblasts; mitotic spindle positioning | jar null mutant analysis with immunostaining of Inscuteable and Miranda; spindle orientation scoring | Dynamic cytoplasmic particles in dividing neuroblasts; enriched during prophase/metaphase | Inscuteable remained apical in 95% of neuroblasts with mislocalized Miranda; spindle misorientation in 21% of jar322 vs 2% controls | Petritsch et al., 2003, Developmental Cell, doi:10.1016/S1534-5807(03)00020-0, https://doi.org/10.1016/S1534-5807(03)00020-0 | (petritsch2003thedrosophilamyosin pages 2-3, petritsch2003thedrosophilamyosin pages 1-2) |
| Required for actin cone organization/stabilization during spermatid individualization; supports formation of dense front meshwork | Testis; spermatogenesis/spermatid individualization | Live and fixed imaging of actin cones; mutant and overexpression analyses; myosin S1 decoration; FRAP of GFP-myosin VI | Localizes to the front of actin cones in individualization complexes | In mutants, cones fail to accumulate sufficient F-actin; overexpression produces bigger cones with more F-actin; FRAP indicates binding for minutes | Noguchi et al., 2006, Mol. Biol. Cell, doi:10.1091/mbc.e06-01-0031, https://doi.org/10.1091/mbc.e06-01-0031 | (noguchi2006myosinvistabilizes pages 1-2) |
| Promotes actin dynamics at membrane-remodeling sites by recruiting/maintaining cortactin and Arp2/3 pathway components | Testis; spermatogenesis membrane remodeling | Colocalization and mutant analysis for myosin VI, cortactin, Arp2/3; genetic interaction with dynamin | Individualization complex / actin structures associated with membrane remodeling | Major actin-structure defects when both dynamin and myosin VI are impaired (no specific percentages in excerpt) | Rogat & Miller, 2002, J. Cell Sci., doi:10.1242/jcs.00149, https://doi.org/10.1242/jcs.00149 | (rogat2002arolefor pages 1-2) |
| The motor head and globular tail cargo-binding domain are both required for cone-front localization and actin-structure specialization; conserved tail binding sites are functionally important | Testis; specialized actin structure assembly | Domain deletions and site-specific mutagenesis in myosin VI; rescue/functional tests in spermatid cones | Cone front dense meshwork | Not numerically stated in excerpt; qualitative separation of localization vs actin-organization functions | Isaji et al., 2011, PLoS ONE, doi:10.1371/journal.pone.0022755, https://doi.org/10.1371/journal.pone.0022755 | (isaji2011myosinviregulates pages 1-2) |
| Important for synaptic development and transmission at the larval neuromuscular junction (NMJ) | Nervous system; larval NMJ synapse development/function | Loss-of-function jar alleles; larval locomotion assays; NMJ morphology; electrophysiology; vesicle marker staining | Synaptic boutons/NMJ; associated with synaptic vesicle pools at bouton periphery | Decreased locomotor activity, reduced NMJ length and bouton number reported; excerpt gives no exact numeric values | Kisiel et al., 2011, BMC Neurosci., doi:10.1186/1471-2202-12-65, https://doi.org/10.1186/1471-2202-12-65 | (kisiel2011myosinvicontributes pages 1-2, kisiel2013analysisofmyosin pages 28-34, kisiel2013analysisofmyosin pages 34-45) |
| Functions as a synaptic vesicle tether/anchor, restraining vesicle mobility and maintaining peripheral vesicle localization | Nervous system; larval NMJ vesicle trafficking | FM dye loading of actively cycling vesicles; FRAP of synaptotagmin-GFP-labeled vesicles in jar mutants | Peripheral region of synaptic boutons; mutant vesicles redistribute throughout bouton | FRAP showed rapid recovery and altered bleach depth in mutants; no exact percentages in excerpt | Kisiel et al., 2014, PLoS ONE, doi:10.1371/journal.pone.0102988, https://doi.org/10.1371/journal.pone.0102988 | (kisiel2014localizationandmobility pages 1-2) |
| Supports planar cell polarity-related trafficking through interaction networks involving Kermit and Vang, implying motor-dependent relocalization of PCP components | Epithelia; planar cell polarity establishment | Genetic screen; pull-down and genetic interaction studies | Intracellular compartments involved in Vang relocalization during PCP establishment | No quantitative values in excerpt | Lin & Katanaev, 2013, PLoS ONE, doi:10.1371/journal.pone.0076885, https://doi.org/10.1371/journal.pone.0076885 | (lin2013kermitinteractswith pages 1-2) |
| Complete myosin VI loss of function is not lethal, but contributes to normal development and fertility-related processes | Whole organism development; viability and fertility | Genetic analysis of jar322 in trans to deficiencies; RT-PCR; westerns; developmental scoring | Broad developmental expression; testes, ovaries, adults examined by western blot | Null animals recovered at lower than expected Mendelian frequency; exact percentage not stated in excerpt | Morrison & Miller, 2008, Genetics, doi:10.1534/genetics.107.085969, https://doi.org/10.1534/genetics.107.085969 | (morrison2008geneticcharacterizationof pages 1-2) |
| Expression is developmentally regulated and tissue-specific, supporting diverse context-dependent roles | Embryogenesis, adult tissues, gonads, nervous system | Western blotting; developmental expression summary from thesis/primary references | Testis, ovaries, neuroblasts, larval brain/NMJ | Peak expression reported during 8–12 h embryogenesis and in adults; six isoforms | Majumdar, 2007, thesis/unknown journal; supporting primary literature summaries | (majumdar2007functionalanalysisofa pages 35-41, majumdar2007functionalanalysisof pages 35-41, majumdar2007functionalanalysisofa pages 54-61) |
Table: This table summarizes primary functional annotation evidence for Drosophila melanogaster jar/jaguar (UniProt Q01989), including molecular function, biological processes, localization, and key assays. It is useful as a compact evidence map linking specific claims to experiments and citation IDs for later narrative synthesis.
References
(morrison2008geneticcharacterizationof pages 1-2): Julie K Morrison and Kathryn G Miller. Genetic characterization of the drosophila jaguar322 mutant reveals that complete myosin vi loss of function is not lethal. Genetics, 179:711-716, May 2008. URL: https://doi.org/10.1534/genetics.107.085969, doi:10.1534/genetics.107.085969. This article has 10 citations and is from a domain leading peer-reviewed journal.
(kisiel2011myosinvicontributes pages 1-2): Marta Kisiel, Debolina Majumdar, Shelagh Campbell, and Bryan A Stewart. Myosin vi contributes to synaptic transmission and development at the drosophila neuromuscular junction. BMC Neuroscience, 12:65-65, Jul 2011. URL: https://doi.org/10.1186/1471-2202-12-65, doi:10.1186/1471-2202-12-65. This article has 27 citations and is from a peer-reviewed journal.
(rogat2002arolefor pages 1-2): Aaron D. Rogat and Kathryn G. Miller. A role for myosin vi in actin dynamics at sites of membrane remodeling during drosophila spermatogenesis. Journal of Cell Science, 115:4855-4865, Dec 2002. URL: https://doi.org/10.1242/jcs.00149, doi:10.1242/jcs.00149. This article has 105 citations and is from a domain leading peer-reviewed journal.
(kisiel2014localizationandmobility pages 1-2): Marta Kisiel, Kristopher McKenzie, and Bryan Stewart. Localization and mobility of synaptic vesicles in myosin vi mutants of drosophila. PLoS ONE, 9:e102988, Jul 2014. URL: https://doi.org/10.1371/journal.pone.0102988, doi:10.1371/journal.pone.0102988. This article has 14 citations and is from a peer-reviewed journal.
(noguchi2006myosinvistabilizes pages 1-2): Tatsuhiko Noguchi, Marta Lenartowska, and Kathryn G. Miller. Myosin vi stabilizes an actin network during drosophila spermatid individualization. Molecular biology of the cell, 17 6:2559-71, Jun 2006. URL: https://doi.org/10.1091/mbc.e06-01-0031, doi:10.1091/mbc.e06-01-0031. This article has 116 citations and is from a domain leading peer-reviewed journal.
(isaji2011myosinviregulates pages 1-2): Mamiko Isaji, Marta Lenartowska, Tatsuhiko Noguchi, Deborah J. Frank, and Kathryn G. Miller. Myosin vi regulates actin structure specialization through conserved cargo-binding domain sites. PLoS ONE, 6:e22755, Aug 2011. URL: https://doi.org/10.1371/journal.pone.0022755, doi:10.1371/journal.pone.0022755. This article has 30 citations and is from a peer-reviewed journal.
(petritsch2003thedrosophilamyosin pages 1-2): Claudia Petritsch, Gaia Tavosanis, Christoph W. Turck, Lily Y. Jan, and Yuh Nung Jan. The drosophila myosin vi jaguar is required for basal protein targeting and correct spindle orientation in mitotic neuroblasts. Developmental cell, 4 2:273-81, Feb 2003. URL: https://doi.org/10.1016/s1534-5807(03)00020-0, doi:10.1016/s1534-5807(03)00020-0. This article has 149 citations and is from a highest quality peer-reviewed journal.
(petritsch2003thedrosophilamyosin pages 2-3): Claudia Petritsch, Gaia Tavosanis, Christoph W. Turck, Lily Y. Jan, and Yuh Nung Jan. The drosophila myosin vi jaguar is required for basal protein targeting and correct spindle orientation in mitotic neuroblasts. Developmental cell, 4 2:273-81, Feb 2003. URL: https://doi.org/10.1016/s1534-5807(03)00020-0, doi:10.1016/s1534-5807(03)00020-0. This article has 149 citations and is from a highest quality peer-reviewed journal.
(lin2013kermitinteractswith pages 1-2): Chen Lin and Vladimir L. Katanaev. Kermit interacts with gαo, vang, and motor proteins in drosophila planar cell polarity. PLoS ONE, 8:e76885, Oct 2013. URL: https://doi.org/10.1371/journal.pone.0076885, doi:10.1371/journal.pone.0076885. This article has 13 citations and is from a peer-reviewed journal.
(majumdar2007functionalanalysisofa pages 35-41): D Guha Majumdar. Functional analysis of drosophila myosin vi in larval neuromuscular junction synapses. Unknown journal, 2007.
(kisiel2013analysisofmyosin pages 28-34): M Kisiel. Analysis of myosin vi in drosophila melanogaster synaptic function and development. Unknown journal, 2013.
(kisiel2013analysisofmyosin pages 34-45): M Kisiel. Analysis of myosin vi in drosophila melanogaster synaptic function and development. Unknown journal, 2013.
(majumdar2007functionalanalysisof pages 35-41): D Guha Majumdar. Functional analysis of drosophila myosin vi in larval neuromuscular junction synapses. Unknown journal, 2007.
(majumdar2007functionalanalysisofa pages 54-61): D Guha Majumdar. Functional analysis of drosophila myosin vi in larval neuromuscular junction synapses. Unknown journal, 2007.