Fmr1Δ50M/Fmr13 mutant females display a strong reduction in fertility. Ovaries from a subset of Fmr1Δ50M/Fmr13 female mutants display developmental defects, including fused egg chambers, aberrant nurse cell numbers, and occasional oocyte misspecification or multiple oocytes per egg chamber.
Fmr13 adult flies show impaired immediate olfactory conditioning memory (learning) in an aversive olfactory memory assay.
Homozygous Fmr13 mutant flies exhibit normal short-term habituation (STH) when flies are exposed to either ethyl butyrate (EB) or CO[]] for 30 minutes. In contrast, Fmr13 mutant flies exhibit a complete block of the long-term habituation (LTH) that is normally seen when flies are exposed to either ethyl butyrate (EB) or CO[]] for 4 days.
Fmr13/+ flies exhibit significant learning and long term memory deficits in a negatively reinforced olfactory learning paradigm. Learning and deficits in Fmr13 heterozygotes are completely rescued upon feeding flies with the pyrrolidinone Rolipram or with 2-Methyl-6-(phenylethynyl)pyridine. Long term memory deficits in Fmr13 heterozygotes are completely rescued upon feeding flies with the pyrrolidinone Rolipram or with 2-Methyl-6-(phenylethynyl)pyridine, but only if the drug is administered both before and after conditioning until testing.
Fmr13/+ flies show increased learning performance with 2 or 4 CS-US pairings, worse performance with 6 or 8 pairings, and similar performance with 12 pairings, compared to controls.
Fmr13/Fmr13 flies have highly penetrant mushroom body defects. Fmr13/+ flies do not exhibit macroscopic mushroom body defects.
Fmr13/Fmr13 flies exhibit reduced adult longevity and severly suppressed locomotor activity, while Fmr13/+ flies exhibit increased locomotor activity.
Mutant larvae have a significantly increased average number of boutons at the neuromuscular junction compared to controls.
The mushroom bodies of mutant pharate adult brains show a high frequency of β-lobe crossover.
Fmr13 mutant larvae exhibit an increase in type Ib and 1s synaptic boutons and branching compared to wild-type controls. Fmr13 mutant larvae exhibit an increase in the length of the primary nerve branch when compared with controls.
Fmr13/Fmr1Δ83M flies have significant locomotor defects (climbing ability) and display excessive grooming behavior compared to rescued controls at 5 days old, getting progressively worse with aging (day 15, 25 and 35). Fmr13/Fmr1Δ83M males show significantly decreased courtship behavior compared to rescued controls.
Homozygous larvae have an increased number of boutons at the neuromuscular junction compared to wild type.
Mushroom body β-lobe axons frequently cross the midline homozygous flies.
Approximately 80% of homozygous adults do not maintain rhythmic locomotion activity under constant darkness conditions.
Mutant males show a reduction in naive courtship activity compared to wild-type males. After training (the males are paired with unreceptive females for an hour), the mutant males do not show a reduction in courtship index at 0-2 or 60 minutes after training when placed with a receptive female, indicating a defect in immediate recall and short-term memory.
Fmr13/Fmr13 mutant flies exhibit a greater frequency of stopping for long lengths of time than wild type. Fmr13/Fmr13 mutant flies tend to spend less time in close physical proximity to other flies, and this is not significantly affected by whether the other flies are also Fmr13/Fmr13 mutants or wild type.
5-day old males heterozygous for Fmr13 do not show any defects in their courtship behavior.
25% of embryos derived from Fmr13/Df(3R)Exel6265 females show a delay in furrow formation compared to controls.
Fmr13/Fmr1Δ50M and homozygous Fmr13 ovaries contain aberrant egg chambers. Some of the abnormal egg chambers display an increased number of germ cells, while others show fewer germ cells per chamber than the normal number of 16. Fmr13 and Fmr13/Fmr1Δ50M mutant germaria contain significantly more mitotic cells than controls. Nurse cells in Fmr13 mutants display increased DNA synthesis throughout oogenesis and exhibit endocycle defects.
Fmr13 follicle cells appear normal.
Fmr13 mutants show a tendency towards elevated response amplification compared to controls. However, there are no statistically significant differences in EJC amplitude between Fmr13 and controls.
Fmr13 mutants show comparable levels of short-term facilitation as wild-type controls.
During prolonged 10-Hz stimulation, Fmr13 mutants maintain a relatively constant 2- to 4-fold increase in EJC response amplitude compared with basal transmission (as in controls).
In response to a HFS, Fmr13 mutants rarely manifest early onset LTF but maintain a low level of augmentation for the duration of the HFS train, as in controls.
During prolonged 20Hz HFS, aproximately 56% Fmr13 mutants manifest periodic cycling of EJC response amplitudes, which begin with enhanced EJC amplitudes, followed by cycling between abnormally low and abnormally high values. During the lulls in EJC response to the HFS, complete loss of EJC response amplitude is not manifested but rather is greatly depressed, but persistent EJCs are recorded: there is no increased incidence of synaptic transmission failure. Additionally, a ramping-up of response amplitude can often be seen during the larger response amplitude phases of the cycling rather than an immediate stepwise increase in response amplitude compared with the LTF threshold.
Fmr13 mutants routinely display the aberrant profile of multiple, enlarged EJC events in response to a single stimulus during a prolonged HFS train. During 20Hz stimulation trains, 88% of Fmr13 mutants manifest this multi-response profile, starting early during the HFS train.
During the post-HFS period, Fmr13 mutants present a hyperexcitable state characterised by multiple, enlarged synaptic responses to a single nerve stimulus.
Fmr13 mutants respond normally to odors and foot shock.
Homozygous Fmr13 or Fmr13/Fmr1B155 transheterozygous mutants show significant defects in 1-d memory after spaced training, but not after massed training.
Homozygous Fmr13 or Fmr13/Fmr1B155 transheterozygous mutants exhibit significant defects in olfactory learning and a β-lobe midline crossing defect.
Heterozygous Fmr13 flies show normal 1-d memory after spaced or massed training.
At relatively low concentrations of cycloheximide or puromycin, 1-d memory after spaced training is significantly ameliorated in Fmr13 mutants (and unaffected in wild-type), while there are no effects on 1-d memory after massed training. There is also a significant improvement in Long-Term Memory with the addition of metabotropic glutamate receptor antagonist MPEP to Fmr13 mutants.
Fmr13 mutants do not display defects in coordinated behavior (such as in a roll-over assay).
Homozygosity for Fmr13 results in a defasciculation phenotype of the termini of the LNv neuron's dorsal projections.
Flies carrying one copy of Fmr1I244N or Fmr1I307N in a homozygous Fmr13 background show no significant increase in the number of type I boutons at the larval neuromuscular junction compared to wild type (muscles 6/7, 12 and 4 from segment A3 have been studied).
Flies carrying Fmr1I244N or Fmr1I307N in a homozygous Fmr13 background show an increased frequency of midline crossing of mushroom body β-lobe neurons compared to controls.
Animals carrying Fmr1I244N or Fmr1I307N in a homozygous Fmr13 background show a significant increase in the percentage of flies that are arrhythmic for locomotor activity under constant darkness conditions compared to controls.
Animals carrying Fmr1I244N or Fmr1I307N in a homozygous Fmr13 background show a reduced courtship index towards virgin females than that seen in wild-type males.
Fmr1- embryos derived from crossing homozygous females and males (the embryos lack maternal and zygotic Fmr1 function) show abnormal pole cell formation. Abnormalities are first seen in nuclear cycle 9-10 embryos, when the polar buds begin to protrude from the posterior end of the embryo; in the Fmr1- embryos the newly formed pole cells are not fully extruded from the surface of the embryo, in contrast to wild type. In nuclear cycle 12-13 Fmr1- embryos the pole cells are not tightly clustered and several of them are separated from the main group. In addition, somatic cells are intermingled with the pole cells in these Fmr1- embryos, in contrast to wild-type embryos.
Stage 12-13 Fmr1- embryos derived from crossing homozygous females and males have an average of 14.5 pole cells per embryo (compared to an average of 22.8 pole cells per embryo in wild type) and there is considerable variation in pole cell number between different Fmr1- embryos (some have no pole cells). The number of germ cells in the coalesced gonad of stage 14-15 Fmr1- embryos is also reduced compared to wild-type embryos., although there is no difference in the number of somatic gonadal precursor cells.
Somatic nuclei of nuclear cycle 13 Fmr1- embryos (derived from crossing homozygous females and males) show a number of abnormalities; they are not always elongated along the apical-basal axis (in contrast to wild-type embryos), often have an irregular shape and are often displaced from the surface of the embryo.
The nuclear division cycles are asynchronous in 25-30% of Fmr1- embryos (derived from crossing homozygous females and males). Abnormal mitotic figures are seen, with defects including lagging chromosomes, chromosome bridges and chromosomal breaks. Centrosome duplication and migration can occur in these embryos, but they can occur even in the apparent absence of a nucleus or DNA and many "free" centrosomes that are not associated with nucleus or DNA are seen. Mitotic nuclei in which all the chromosomes appear to be moving towards one of the centrosomes are also seen.
68% of embryos produced by females with Fmr13 germline clones are devoid of pole cells and the remaining 32% contain ~22 pole cells. 597% of these embryos are arrested at embryonic cycle 1 or are unfertilized, and 9% are arrested before cycle 8. In addition, these embryos show severe defects in chromosomal segregation, nuclear distribution and supernumerary mitoses. Among mitotically normal embryos from Fmr13 mothers at cycle 9-14, only 3% of them had no pole cells and 20% of them contained fewer than ten pole cells, yet 77% displayed approximately
normal numbers of pole cells.
Fmr13/Df(3R)Exel6265 females produce morphologically normal eggs at similar rates to wild-type females when crossed to wild-type males. However, fewer of the embryos from Fmr13/Df(3R)Exel6265 females hatch. The viability of these embryos is determined by the maternal genotype.
Embryos produced from Fmr13/Df(3R)Exel6265 females and wild-type males exhibit a subtle defect in the duration of nuclear cycles 12 and 13, and a fully penetrant cellularisation phenotype. Approximately 75% of the embryos display a significant reduction in the rate of furrow ingression, whereas the remaining 25% display dramatic cellularisation defect characterised by uneven furrow ingression.
A significant number of Fmr13/Fmr13 egg chambers have either reduced or increased numbers of germline cells. In addition, almost 10% of these egg chambers contain presumptive oocytes with polyploid oocyte nuclei or two oocytes located at opposite poles.
The learning ability of Fmr13 mutant males during the training phase of conditioned courtship is not impaired compared to wild-type but they display immediate recall (0-2min) memory defects.
Fmr13 homozygous larvae exhibit hyperplasia of neuromuscular junctions: The number of boutons per neuromuscular juntion is significantly increased.
Slightly over 65% of homozygous Fmr13 mutants exhibit severe midline crossing in the β-lobe of the mushroom body (defined as a densely strained band equal to or greater in width and thickness than those of the adjacent β-lobes). The rest appear phenotypically normal. No sexual dimorphism in penetrance or expressivity is found.
Slightly over 70% of transheterozygote Fmr13/Fmr1Δ113M mutants exhibit severe midline crossing in the β-lobe of the mushroom body. Just under 10% of these mutants exhibit moderate midline crossing (defined as when the thickness of the fiber bundle crossing the midline is considerable but less than the width of the β-lobe termini).
Slightly over 85% of transheterozygous Fmr1Δ83M/Fmr13 mutants exhibit severe midline crossing in the β-lobe of the mushroom body (defined as a densely strained band equal to or greater in width and thickness than those of the adjacent β-lobes). Approximately 5% exhibit moderate midline crossing (defined as when the thickness of the fiber bundle crossing the midline is considerable but less than the width of the β-lobe termini), with another 5% exhibiting mild midline crossing (defined as when a thin band of fibers cross the midline). No sexual dimorphism in penetrance or expressivity is found.
In fewer than 10% of cases, transheterozygous Fmr1Δ83M/Fmr13 mutants exhibit misdirected or missing α-lobes.
Single cell mutant clones in the mushroom body (in a wild-type background) produce additional cell body processes compared to wild-type single cell clones (converting the characteristic unipolar mushroom body neurons seen in wild-type into multipolar neurons); there is a 3-fold increase in the number of cell body processes in the mutant cells. The mutant cells show a more complex and disordered dendritic structure compared to wild type; primary dendrites display clear secondary branches and the fine dendritic processes that are normally restricted to the termini spread aberrantly along the primary branches. Single cell mutant γ neurons in the mushroom body always have significantly increased axonal branching and significantly more and longer axonal branches than control cells. The large, extra branches do not follow the main axon trajectory, but instead extend in apparently random directions to invade inappropriate territory.
Fmr13/Fmr14.L wandering larvae have defects in crawling behaviour; they spend significantly less time on linear locomotion than wild-type control larvae and the average duration of linear locomotion is reduced compared to controls. The average direction change (direction change is defined as the difference in direction from one frame to the next in the analysis) is increased compared to controls.
Flies show no visible phenotypic abnormalities. Phototactic and chemotactic abilities are normal. Mutant flies are arrhythmic with respect to locomotor behavior as measured in an actogram and periodogram and show disrupted eclosion periodicity. General motor functions and locomotor abilities appear normal. Mutants can be driven to display activity rhythms in the presence of light:dark cycles. Mutant males spend significantly less time than wild type engaged in courtship, and fail to engage in advanced courtship behavior - progressing no further than following/tapping. Adult brains have wild type numbers of small and large ventral lateral neurons, and projection to the optic lobes via posterior optic tract and to the ipsilateral dorsal protocerebrum are present, but a high frequency of collateral branches emanate from these axons in mutant brains. Termini are unusually arborized. Mushroom bodies of mutant brains do not appear to be morphologically different from those of wild type.