heterozygosity does not significantly affect the mitotic index in the adult midgut epithelium, as compared to controls.
Ostia cells in wgl-12
embryos shifted to restrictive temperatures after heart specification show variable phenotypes in terms of cell size and the ostia cells are rounder than wild-type.
Homozygous embryos shifted to the restrictive temperature at 9.5 hours after egg laying (AEL) develop a diverse denticle belt pattern, but show incomplete specification of the naked cuticle zone. Homozygous embryos shifted to the restrictive temperature at 10 hours AEL have an almost normal denticle pattern.
Mutant third instar larvae raised at 29[o]C show a reduction in neuromuscular junction size compared to controls.
flies show loss of indirect flight muscles.
embryos show a loss of neurons derived from SOPs in the posterior of the parasegment: the vbd neuron is lost in 100%, the class III lost in 85% and class II neurons in 73% of parasegments. Both class IV neurons, vdaB and v'ada, always form. Multidendritic neuron loss in wgl-17
mutants is always preceded by the loss of posterior SOPs: all four SOPs are lost in 45%, three are lost in 35%, and two lost in 20% of parasegments.
The anterior compartment of all abdominal segments fail to generate characteristic cuticle and bristles in homozygous wgl-12
mutants that are kept at the restrictive temperature during pupal development.
Compared with heterozygous siblings, posterior compartments of all abdominal segments in both sexes are several cells wider in homozygous wgl-12
mid-pupal stage flies switched to the non-permissive temperature exhibit less cell death and a higher interommatidial precursor cell (IPC) number per hexagon than flies maintained at the permissive temperature.
Neuromuscular junction development is normal in wgl-12
The nuclear size of mutant cells in the proximal region of the salivary gland is larger than that of wild type proximal cells. Thus, the normal difference in size between proximal and distal salivary gland cells is small in wgl-12
Shifting of heterozygous wgl-12
larvae from 17[o]C to 29[o]C for 16hrs prior to dissection completely prevents the increase in ghost bouton formation seen in controls upon spaced 5X K[+] depolarisation. mEJP (spontaneous excitatory potentials) frequency is also defective upon spaced 5X K[+] depolarisation. 0 K[+] wgl-12
/+ larvae have mEJP frequency and amplitude, as well as EJP amplitudes, indistinguishable from controls.
The maxillary segments of wgl-12
mutant embryos are smaller than those of wild-type embryos.
C mutant embryos exhibit a complete loss of cI and cII cluster of slou
expressing muscle founder cells. At 18o
C none are missing. When mutant embryos are shifted from 18o
C to 25o
C at mid-stage 11 (12 hours after egg laying (AEL)) a complete loss of cluster II slou
expressing muscle founder cells is seen - cluster I cells are unaffected. When mutant embryos are shifted from 18o
C to 25o
C at late-stage 11 (12 hours AEL), an occasional loss of cluster II slou
expressing muscle founder cells is seen - cluster I cells are unaffected.
Mutant embryos have a "lawn of denticle" phenotype at the restrictive temperature.
larvae that are grown at the restrictive temperature prior to and during cell shape changes in the disc, epithelia develop severely reduced wing and leg discs compared to heterozygous controls. The epithelial morphology of these discs is normal.
Differentiated filzkorpers are present in wgl-12
embryos that have been maintained at the restrictive temperature from 5-8 hours of development despite severe segment polarity defects. However, the filzkorper is often at an abnormal position due to the absence of attachment to the disorganised tracheal network.
animals raised at 18o
C until 28 hours after puparium formation (developmentally equivalent to approximately 17 hours APF at 25o
C) and then shifted to 25o
C for 7 hours show a small but significant decrease in cell death in the pupal retina.
In mutant embryo that have been shifted-up to the non-permissive temperature for 60 minutes from late stage 10 to stage 11, misrouting of the visceral branch (VB) is seen towards the posterior region of the visceral mesoderm (VM) of each parasegment.
Early lack of wg
function (using temperature shift) results in a dramatically smaller hindgut than normal, while elimination of wg
function during stage 10 or later allows essentially normal hindgut elongation.
Raising developing animals to the restrictive temperature after the specification of wing discs causes no change in wing disc formation.
Homozygous females raised at 18oC (to obtain adults) and then shifted to a restrictive temperature (30oC) for a week show defects in the ovary; the germarium has many more germline cysts (20.0 +/- 3.8) compared to wild type (7.9 +/- 1.2). Two 16-cell cysts are sometimes packed into an egg chamber because of over-crowded germline cysts or defects in follicle cells.
Removal of wg
function before 72 hours after egg laying in wgl-12
animals results in truncated legs which lack the distal parts and have ventral patterning defects. wgl-12
animals shifted to the restrictive temperature approximately 84 hours after egg laying have legs with ventral patterning defects but otherwise intact proximal-distal organisation.
mutants are grown at the permissive temperature until 3rd instar larval stage then switched to restrictive temperature, defects are seen in target dependent synapse formation. In the wild-type, about half of type I boutons are formed during the last day of larval development. In mutants, neuromuscular junction (NMJ) expansion is dramatically reduced resulting in an over 25% decrease in the number of boutons compared to wild-type. This is a 50% reduction in the number of boutons that should have formed during the last day of the third instar larval stage. The filamentous bundles of microtubules seen in wild-type terminal boutons are frequently splayed or disintegrated, the microtubule loops seen in paused growth cones are seen less frequently than seen in wild-type. Boutons are also irregular in shape. Many boutons are noticeably larger than wild-type, they deviate greatly from the normal elliptical shape, display a rough outline and often do not show a clear separation from neighbouring boutons. Type II and type III boutons are not affected in these mutants. Boutons in temperature shifted wgl-12
mutants can be divided into three categories. The first (33%) category have boutons thoroughly filled with synaptic vesicles and are completely devoid of both active zones (both the electron dense thickening of pre- and postsynaptic membranes and the T bar) and mitochondria. post-synaptically, these boutons also completely lack Subsynaptic Reticulum (SSR). These are located most frequently at the distal region of a branch and so are likely to have formed later in neuromuscular junction development. The second group of boutons (33%) are localised at intermediate positions within a branch. Most of these boutons (around 60%) contain active zones with abnormally shaped T bars, appearing as amorphous dense areas or contain aberrantly shaped stems with little ort no bar. The post-synaptic area immediately apposed to active zones are also dramatically altered. The postsynaptic pocket is enlarged and often contain a number of membranous structures. These large pockets give boutons an irregular appearance, in which regions of the presynaptic compartment appear detached from the SSR. The rest of the postsynaptic areas appears relatively normal, although the number of SSR layers is significantly reduced. In addition these boutons have fewer mitochondrial profiles. In the last category (33%) boutons are indistinguishable from wild-type, although most of these boutons are located closer to the motor neuron's initial point of contact with the muscle.
animals upshifted to the restrictive temperature during the late second or early third instar develop into pharate adults with hinge defects that consistently show reductions of axillary sclerite 3.
wing discs shifted to the restrictive temperature for 24 hours at the beginning of the second larval instar show a profound wing to notum transformation.
When raised at 29o
C the HVM does not differentiate properly. Loss of wg
after the initial HVM migration over the hindgut ectoderm does not prevent HVM cells from developing further.
embryos raised at the restrictive temperature from 8 hours of development show a reduction in the number of 4o
denticle rows from 8-9 to 4-5 in the dorsal epidermis of the embryo. The anterior half of the parasegment is unaffected (an expansion of 3o
denticles is never seen).
Defects in tracheal cell invagination are seen in mutant embryos shifted to the restrictive temperature 11 hours after egg laying (AEL). Temperature shift at 16 hours AEL or earlier results in a number of tracheal defects; the dorsal trunk is partially lost or fails to migrate and fuse and the fusion of the lateral trunk is also inhibited, while the migration of the visceral branch is relatively normal. Temperature shift later than 17 hours AEL results in defects in the dorsal branch; the dorsal branch fails to fuse at the dorsal midline and often curves in the anteroposterior direction to make contact with the tip of adjacent dorsal branch segments. These migration defects are often associated with the loss or gain of terminal branches.
Mutant embryos shifted to the restrictive temperature from early stage 11 to stage 13 show severe defects of lateral trunk and dorsal branch fusion, as well as defects in ganglionic branch guidance in the tracheal system. However, signs of dorsal trunk (DT) differentiation are generally seen and the DT is continuous between metameres.
Embryos younger than 4 hours old that are shifted up to the restrictive temperature fail to develop Malpighian tubule tip cells. Embryos older than 4 hours old that are shifted down from the restrictive temperature fail to develop Malpighian tubule tip cells. If wg
is removed (by heatshocking wgl-12
flies) 5 or 6 hours after egg laying but before cell division ceases in the Malpighian tubules, the final tubule cell number is reduced compared to wild-type.
embryos in which wg
function is eliminated after 8 hours after egg laying, the anterior en
-expressing cells in each segment incorrectly adopt a denticle fate.
Heterozygous embryos kept at the restrictive temperature are patterned normally. Homozygous embryos kept at the restrictive temperature have a uniform lawn of type 5 denticles.
Temperature up-shift experiments leads to loss of smooth cell fates in the embryonic epidermis.
homozygotes grown at the non-permissive temperature (25o
C) show a replacement of naked cuticle with denticles along the length of the ventral surface. wgl-12
homozygotes grown at an intermediate temperature (20o
C), leading to partial loss of wg
function, have cuticles with reductions in naked cuticle and a segment polarity defect.
Ectopic differentiation is seen along the dorsal-anterior margin of the eye disc in homozygotes raised at the restrictive temperature for 36 hours during the larval stage.
Larvae shifted to the restrictive temperature 24 hours prior to dissection exhibit limited ectopic differentiation at the dorsal margin of the eye disc, larvae shifted 48 hours prior to dissection exhibit extensive ectopic differentiation.
function at 24-30 hours of disc development abolishes both G1 and G2 arrest.
Homozygous embryos raised at the restrictive temperature lack most eve
-expressing pericardial cells and DA1 muscles.
Temperature upshift at stage 9, 4.5 hours after acridine orange injection, reveals massive cell death throughout the embryo. The most obvious effect is seen at the tip of the germ band and in the epidermis, though not all regions of the epidermis are affected. Temperature upshift at stage 11, 6.5 hours after acridine orange injection, causes significant increase in cell death appearing as stripes about 2-3 cells in diameter in the anterior half of each segment, near the segment border, during stages 12-14.
The second midgut constriction fails to form in homozygous embryos raised at the restrictive temperature.
Specification of all cardiac lineages is abolished in homozygous embryos shifted to the non-permissive temperature at 3.5 hours AEL. Embryos shifted to the non-permissive temperature at 7.5 hours AEL have a disrupted heart pattern.
Temperature sensitive-mutation. The wing pouch is reduced in size in discs shifted to 22oC. Larvae shifted to 22oC during the early third instar stage do not survive to adulthood, and give rise to animals with small wings that do not have wing margins.
embryos in which wg
function is eliminated 8 hours after egg laying have an extra denticle row anterior to the normal first row.
Homozygotes which are shifted to the restrictive temperature after 8 hours of development give rise to larvae with abnormal denticle belts. Cores of normal denticle belts in which rows 1-5 are unaffected are present, however additional denticles are present both anteriorly and posteriorly to these belt cores, widening the denticle belts, and leaving little naked cuticle between them. The anterior additional denticles are of the row 1-4 type, and the posterior additional denticles are of the row 6 type.
Stage 12 wgl-12 ptc7
double mutants embryos exhibit ectopic dorsal median cells that have aberrant segmental organisation. By stage 15 dorsal median cells have expanded along the entire anterior/posterior length of the midline.
In the temperature sensitive combination wgl-12
, loss of wg
activity shortly before dsh
is overexpressed completely abolishes the ectopic bristle response.
Contrary to previous reports, the activity of wgl-12
C is not wild type. Mutants show reproducible phenotypes dorsally (reduction in the number of rows of 4o
hairs) and mild but reproducible phenotypes ventrally (extra denticles near the midline). If wg
function is abolished at 6hrs AEL, nearly all 4o
cell types are lost. Shifts after 9hrs cause phenotypes identical to those raised at 16o
cell types are unaffected.
Hinge defect is indistinguishable from wgspd-fg
larvae grown at the restrictive temperature result in heads that lack both the lateral and mediolateral structures causing the ocelli to be directly adjacent to the compound eyes. Ocellar cuticle and the ocelli are larger than wild type.
Homozygotes at 17oC exhibit an almost wild type phenotype. Third instar larvae raised at the restrictive temperature, 25oC, fail to eclose and exhibit missing tergites and sternites. Temperature shift experiments reveal the temperature sensitive period for bristle formation is 15-20hr APF.
Flies exposed to the restrictive temperature for 24 hours from late second instar exhibit severely reduced wings. SerBd-3
flies raised at 17o
C have wings reduced to a stump.
Clones that cross the wing dorsal/ventral boundary can cause extensive non-autonomous loss of wing tissue. Clones restricted to one side do not cause nicking of the wing.
Embryos were allowed to develop at the permissive temperature for 8 hours to allow normal segmentation, then shifted to the restrictive temperature for 8 hours to abolish wg
function in the midgut before a shift back to the permissive temperature. Mutant larvae did not grow and died within a few days The characteristic banana shape of the copper cells could not be found in the midgut under UV light. Embryos kept at 15o
C during mid-embryogenesis have good copper cells. At 17.5o
C the midguts are not normal, copper cells are small.
function is inactivated in the developing eye for two days after the late second instar, an ectopic furrow is induced proceeding down from the dorsal margin. The ectopic furrow produces well-spaced clusters of developing neurons and confers cell-cycle synchrony, but is not normal with respect to ommatidial rotation. Loss of wg
in second instar discs cannot induce furrows. Once the furrow initiates it extends along the dorsal margin, and to some extent along the ventral margin, but does not occupy all of the dpp
expression domain. That part of the eye-antennal disc that will give rise to the dorsal cuticle and ocelli is deleted. When wg
function is inactivated for one day after the late second instar a few adults survive and have distorted heads with large eyes and deleted ocelli and antennae. When wg
function is removed the clusters formed by the endogenous furrow rotate normally, but clusters formed by the ectopic furrow fail to rotate.
When raised at a non-permissive temperature the stomodeum fails to invaginate properly. Pulsed temperature shift experiments produced larvae that move normally but cannot feed due to a specific defect, the cardiac arrest phenotype, foregut cells are clustered at the top of the proventriculus and cannot migrate inside to form the cardiac valve. Consequently food cannot be efficiently transported into the midgut resulting in an engorged oesophagus.
At the restrictive temperature (25oC) photoreceptor differentiation progresses medially from the dorsal and central margin as well as anteriorly from the posterior margin.
Heart development is severely affected when the temperature is shifted 4 to 4.5hr of development, the number of pericardial cells is almost halved compared to wild type embryos and embryos exhibit weak segment polarity defects.
Viable and almost wild type at 17oC, homozygotes have a narrow wing margin.
Temperature shifts after 96 hours AEL, or at the time of pupation (120-124 hours AEL, or 0-4 hours APF) produce pharate adults with a narrow wing margin phenotype. Most bristles are missing and the remaining ones are intermingled in two or even one row, instead of three rows interspersed by trichomes. A 24 hour pulse, from 96-120 hours AEL produces weaker narrow margin phenotypes. However shifts shortly before 96 hours AEL result in pharate adults in which the wing lacks all margin characters: every bristle is missing, though veins and sensillae are present and patterned. There is no notching of the wing margin.
Distal structures of the leg and antenna fail to develop at 29oC.
When newly hatched wgl-12
larvae are shifted to a non-permissive temperature the normal crescent-shaped neuropil of the medulla, the target for retinal axons R7 and R8, collapsed into a small circular remnant. The number of developing ommatidia is reduced. Later inactivations of wg
produce less severe reductions in the number of developing ommatidia, the size of the lamina and the size of the medulla neuropil. In all cases the reduction of the structures is from their dorsal and ventral extents. The number of outer proliferative center cells incorporating BrdU is markedly decreased in the Fas2
expressing domain of wg
early third instar brains.
Somatic muscles of embryo are deranged. Myotubes are scattered along the ectoderm without any orientation. They are often very elongated. At stage 12, ventral muscle precursors as visualized by staining for nau
RNA, are missing, while dorsal and lateral rows are present.
Behaves as wild type at 16-18oC, but is non-functional at 25-29oC.
Used to generate "wg-" embryos in study on neuroblast specification and formation. Embryos raised at restrictive temperature have identical pattern of all molecular markers studied at early stage 9, so wg is not required for the formation or initial segregation of the S1 neuroblasts. Shortly after this differences in pattern of e.g. runt expression in neuroblast row 4, indicate that mutant phenotype is becoming detectable. All neuroblast and ganglion mother cell markers support the theory that neuroblast NB4-2 transformed to NB3-2. The wg gene product was shown to be required for nearly one quarter of all neuroblasts that generate the CNS.
Ba is not expressed in the leg primordia of embryos raised at 29oC. Removing wg activity at any time prior to the activation of Ba blocks subsequent Ba expression. Ba remains dependent on wg activity until the Ba early enhancer has been activated and then rapidly becomes wg independent.
The heteroallelic combination wgl-12
has been used as a temperature sensitive genotype to study the requirement for wg gene product in the development of the leg, wing and haltere imaginal discs: wg is required only during the second larval instar in the wing and haltere discs, whereas legs are affected by temperature shifts at all times up until mid-third instar larva.
A maximum of 5 of the 11 notal bristles (the posterior postalar, and the anterior and posterior dorsocentral and scutellar bristles) is sensitive to non-permissive conditions in wgl-12
. Dorsocentral, scutellar and posterior postalar bristles are not rescued by down shift after the late third instar. The sensory bristles of the wing are also temperature sensitive during the late third instar and early prepupal stages: the wing blade is of a normal size but is devoid of marginal structures. In wild type discs, but not in wgl-12
discs, cells near the presumptive wing margin stop DNA replication shortly before pupariation. The sensory mother cells of the posterior post alar, and the anterior and posterior dorsocentral and scutellar sense organs are absent from wgl-12
Mirror phenotypes result if the wg gene is active during early embryonic development (up to 6 hours) but not later. The result is the same whether the gene product is ubiquitous (wghs.P) or normally localised (wgl-12).
Temperature shifts to the restrictive temperature at or before gastrulation result in a wg
null phenotype: ventral patterning is disrupted, there are no lateral pattern elements and there is only limited patterning of the dorsal surface in the larval cuticle. In embryos shifted to the restrictive temperature at 4 hours after egg laying (AEL), lateral pattern elements are present, but their arrangement is compromised by defects in dorsal closure. In rare embryos where dorsal closure has occurred normally, lateral and dorsal pattern elements are seen, in embryos shifted to the restrictive temperature at 4.25 hours AEL. Embryos shifted down to the permissive temperature at 4 hours AEL have wild-type cuticle. Those shifted down at 4.5 hours AEL have defective dorsal and lateral patterning, while ventral patterning is not greatly affected. Embryos shifted in temperature at different times after 5 hours AEL show a progressive transition from the ventral cuticle null phenotype (symmetrical groupings of a single type of denticle) to an asymmetric pattern of different denticle types (all wild-type denticle belts are present and arranged correctly in the anterior portion of each segment, but the posterior portion is occupied by denticles of indeterminate type).
Moderate segment polarity phenotype.
C, homozygous wgl-12
embryos develop normally and hatch to produce larvae that have a wild-type cuticular pattern, but these mutants do not survive to become adults. wgl-12
mutants, however, do survive at 16.5o
C to become phenotypically wild-type adults (Baker, 1988a). hs lethal (embryo)