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General Information
Symbol
Dmel\Nmnat2
Species
D. melanogaster
Name
FlyBase ID
FBal0198133
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Allele class
Nature of the Allele
Allele class
Mutations Mapped to the Genome
 
Type
Location
Additional Notes
References
point mutation
Nucleotide change:

G24946169A

Amino acid change:

W244term | Nmnat-PA; W244term | Nmnat-PB; W213term | Nmnat-PC; W213term | Nmnat-PD

Reported amino acid change:

W213term

Comment:

G to A nucleotide change at the second or third position of the Trp codon leads to a nonsense mutation (exact site of mutation unspecified). Site of nucleotide substitution in mutant inferred by FlyBase based on reported amino acid change.

Associated Sequence Data
DNA sequence
Protein sequence
 
 
Progenitor genotype
Cytology
Nature of the lesion
Statement
Reference

Amino acid replacement: W213term.

Expression Data
Reporter Expression
Additional Information
Statement
Reference
 
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Associations
Disease Ontology (DO) Annotations
Models Based on Experimental Evidence ( 0 )
Disease
Evidence
References
Modifiers Based on Experimental Evidence ( 0 )
Disease
Interaction
References
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
 
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description
Statement
Reference

Flies with eyes that are mostly homozygous for Nmnat2 (due to somatic clones induced using Scer\FRT and Scer\FLP1ey.PN) with heterozygous patches are smooth with a normal external morphology. Electroretinogram (ERG) recordings from such eyes belonging to young mutants show reduced depolarization and on/off responses. Transmission electron microscopy of lamina synapses from 1-day-old flies with these clones reveal morphological defects; the laminae are disorganized, with various numbers of terminals. The terminals contain a fragmented cytoskeleton and misshapen membrane organelles. In presynaptic terminals, the T-bars are amorphous and less electron dense compared to wild type, but they are surrounded by clusters of normally sized synaptic vesicles. However, the size of the T-bar profile, measured by the width of platforms is significantly reduced compared to wild type.

Eyes with Nmnat2 somatic clones show early-onset neuronal degeneration. At 96h after puparium formation (APF), the size of rhabdomeres are reduced with respect to wild type, although the development of photoreceptor terminals is mostly normal. As the mutant photoreceptors age, the number of recognizable terminals per cartridge declines and the active zone structure becomes smaller and amorphous. In 2-day-old mutants, the rhabdomeres are more reduced in size compared to in the 96h APF flies and large vacuoles are abundant in individual ommatidia; by 28 days, the rhabdomeres are barely recognizable. The magnitude of the depolarization and the on/off transients in ERG recordings also decline with age.

Flies with Nmnat2 clones in the eye show a high level of light-induced degeneration. When flies are raised in the dark, at 1 day of age rhabdomere size and photoreceptor terminal morphology is comparable to wild type. In contrast, 1-day-old flies raised in a 12-h light/dark cycle show a dramatic reduction of rhabdomere size. At 10 days of age, dark-reared flies show a much less severe phenotype than those raised in a light/dark cycle, although these flies still exhibit some sign of neurodegeneration, such as small rhabdomeres, the presence of vacuoles in the cell body, and ultrastructural defects in the photoreceptor terminals.

External Data
Interactions
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Phenotype Manifest In
Suppressed by
Statement
Reference
NOT suppressed by
Additional Comments
Genetic Interactions
Statement
Reference

In norpA36; Nmnat2 double mutant photoreceptors, the neurodegeneration seen in Nmnat2 single mutant receptors is partially suppressed; the overall ommatidial structure is better organized, the vacuoles in the ommatidia are smaller and the loss of rhabdomeres is reduced.

Xenogenetic Interactions
Statement
Reference

Expression of BacA\p35Scer\UAS.cHa under the control of Scer\GAL4GMR.PF in Nmnat2 photoreceptor clones does not suppress the Nmnat2 phenotype.

Complementation and Rescue Data
Images (0)
Mutant
Wild-type
Stocks (1)
Notes on Origin
Discoverer

Selected as: a mutant with abnormal synapse structure in R1-R6 terminals and abnormal ERG responses from an "eyFLP" screen of flies with grossly normal eye morphology that phototax poorly.

External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (3)
Reported As
Name Synonyms
Secondary FlyBase IDs
    References (3)