Mitochondrial DNA mutations in Japanese patients with optic neuropathy unassociated with a mutation at nucleotide position 11,778

We examined for mitochondrial DNA (mtDNA) mutations at nucleotide positions(nt) 3460, 14,484, 9438, 9804, and 15,257 in ten Japanese patients with idiopathic optic neuropathy unassociated with a mutation at nt11,778. The mtDNAs were amplified by polymerase chain reaction (PCR), the products were digested with restriction enzymes, and the sizes of the fragments were analyzed on 8% polyacrylamide gel. Of the ten patients, one had an mtDNA mutation at nt3460 and another patient had a mutation at nt14,484. We suggest that mtDNA mutations in Japanese patients with optic neuropathy unassociated with a mutation at nt11,778 should be further investigated.

Alteration of cell fate by ectopic expression of Drosophila glial cells missing in non-neural cells

The glial cells missing (gcm) gene encodes an essential transcription factor that converts neuronal precursor cells to glial fate in the Drosophila nervous system. In this study, we tested effects of gcm ectopic expression on fate of non-neural cells. When gcm expression was continuously induced in epidermal cells from around stage 9, these cells started to exhibit mesenchymal cell morphology at stage 13, which was preceded by the onset of expression of Repo, a glial marker. The morphological change was coincident with loss of expression of an epidermal cell-adhesion molecule. In addition to the epidermis, fate of mesodermal cells was also affected by gcm ectopic expression. These findings suggest that gcm can convert gene expression and cell morphology even outside the neuroectoderm.

Missense mutations in the PAX6 gene in aniridia

PURPOSE

Aniridia is caused by a mutation of the PAX6 gene. Haploinsufficiency of the gene product is thought to result in the aniridia phenotype, because most mutations thus far detected have been large deletions encompassing the entire gene and nonsense, frameshift, or splice errors that result in premature translational termination on one of the alleles. Only two missense mutations have been detected in aniridia pedigrees, each of which occurs in its paired domain or homeodomain. In this study, four novel missense mutations were found in three aniridia pedigrees.

METHODS

Polymerase chain reaction-single-strand conformation polymorphism analysis and sequencing of the PAX6 gene were performed using genomic DNA of three aniridia pedigrees and more than 100 healthy control subjects.

RESULTS

Three mutations occurred in the N-terminal subdomain of the paired domain, namely N17S, I29V, and R44Q, the first two of which were detected on the same allele of one patient. The other mutation (Q178H) was in the linking portion of the paired domain and homeodomain.

CONCLUSIONS

These missense mutations give rise to haploinsufficiency by another route, because the missense mutations presented here resulted in an aniridia phenotype indistinguishable from that caused by a heterozygous deletion of the entire PAX6 gene.

Arg124Cys mutation of the betaig-h3 bene in a Japanese family with lattice corneal dystrophy type I

To characterize severe lattice corneal dystrophy, we analyzed the betaig-h3 gene, clinical features, histological findings, and genotype-phenotype correlation in an affected Japanese family. Deoxyribonucleic acid was extracted from leukocytes in 16 members (12 affected and 4 unaffected) of a Japanese family with lattice corneal dystrophy type I. Exon 4 of the betaig-h3 gene was amplified and analyzed using molecular biological methods. Clinical and pathological data were also collected. We found a heterozygous point mutation that causes the disease phenotype. It was a single base-pair transition leading to an amino acid substitution (CGC-->TGC, Arg124Cys). The phenotypic variation within families was not recognized. The affected members in the pedigree demonstrated severe visual disturbance in the third decade and required keratoplasty. Histopathological examination revealed amyloid deposits consisting of short and thin amyloid fibers and lattice corneal dystrophy type I. The heterozygous Arg124Cys mutation reported in Caucasian lattice corneal dystrophy caused severe lattice corneal dystrophy consisting of short and thin amyloid fibers in a Japanese family. Based on our study of many members of the family, we are able to construct the natural course of this disorder from its earliest clinical findings through its late manifestations.

A new L527R mutation of the betaIGH3 gene in patients with lattice corneal dystrophy with deep stromal opacities

Mutations in the betaIGH3 gene on chromosome 5q31 cause five distinct autosomal dominant corneal dystrophies: granular Groenouw type I, Reis-Bücklers', lattice type I and IIIA. and Avellino corneal dystrophies. We present here a new mutation of the betaIGH3 gene in patients with late-onset lattice corneal dystrophy manifest as a deep stromal opacity. To test the previously reported R124C, R124H, P501T, R555W, and R555Q mutations of the betaIGH3 gene, 30 patients and 11 normal relatives from 16 independently ascertained families with lattice corneal dystrophy, 49 patients and 12 normal relatives from 40 independently ascertained families with other corneal dystrophies, and 40 unrelated normal volunteers, were analyzed. A L527R (CTG/CGG) mutation of the betaIGH3 gene was found in 6 unrelated patients with lattice corneal dystrophy. A retrospective review of the patients' records showed that the opacities were deep in the stromal layer and of late onset. The mutation was a heterozygous single base-pair transversion from T to G of the second nucleotide position of codon 527. This caused the substitution of arginine for leucine. These six patients did not have mutations in codons 124, 501, or 555. The L527R mutation was not detected in the other corneal dystrophies or 40 normal volunteers. Although phenotypic variations in the size and shape of the deposits were found, all patients with the L527R mutation showed deposits deep in the stromal layer. We conclude that there are now at least six different mutations that have been detected in the betaIGH3 gene on chromosome 5q31 and that lead to corneal dystrophy.

Japanese juvenile retinoschisis is caused by mutations of the XLRS1 gene

We investigated the XLRS1 gene in Japanese patients with retinoschisis (RS). All exons of the XLRS1 gene were sequenced in 14 males, including a pair of monozygotic twins, from 11 individual families with RS and five of their mothers who are asymptomatic but diagnosed as carriers. Six kinds of missense mutations and a nonsense mutation, including six novel mutations, were detected in all 14 patients and carriers. Mutations in the XLRS1 gene are also responsible for RS in non-Caucasian patients. Most Japanese RS cases are caused by an XLRS1 gene defect. A novel mutation, Glu72Lys, was found in four families, suggesting a common mutation in the Japanese population. Clinical features of RS patients with both the Glu72Lys and Pro193Leu mutations indicate that a genotype-phenotype correlation is not recognized in RS.

Analysis of peripherin/RDS gene for Japanese retinal dystrophies

We studied 133 Japanese patients with retinal dystrophies to detect peripherin/RDS (retinal degeneration slow) gene defects. The patients analyzed included 52 with autosomal dominant retinitis pigmentosa, 36 with autosomal recessive retinitis pigmentosa, 3 with simplex retinitis pigmentosa, 12 with cone-rod dystrophy, 5 with rod-cone dystrophy, 3 with vitelliform macular dystrophy (Best's disease), 4 with macular dystrophy, 2 with cone dystrophy, 2 with fundus flavimaculatus, 2 with fundus albipunctatus, and 12 with retinitis pigmentosa with macular degeneration as well as 40 unrelated normal persons. Three exons of the peripherin/RDS gene cut into 150-200 base-pair fragments were amplified by polymerase chain reaction and screened by single-strand conformation polymorphism. The DNA fragments with any suspected variations were directly sequenced. Eight point mutations were detected. Among them, two missense mutations at codons 304 and 338 result in an amino acid substitution of glutamine for glutamic acid and aspartic acid for glycine, respectively. However, they were not cosegregated with the diseases, and these mutations were also commonly found in normal controls. For these controls, the proportion of transversion from G to C at codon 304 (GAG-->CAG) and transition from G to A at codon 338 (GGC-->GAC) were 0.192 +/- 0.045 and 0.173 +/- 0.053, respectively. Our results suggest that a peripherin/RDS gene mutation might be rare in Japanese patients.

Homozygotic patient with betaig-h3 gene mutation in granular dystrophy

PURPOSE

This study investigated patients with granular dystrophy and identified a homozygotic patient and his family with a mutation in the betaig-h3 gene.

METHODS

Genomic DNAs were extracted from leukocytes of the peripheral blood of the proband, his parents, and his grandmother. All had granular dystrophy. Genomic DNAs from 50 unrelated normal volunteers were used as controls. Exon 4 of betaig-h3 gene was amplified and analyzed by direct sequence. Clinical data were collected.

RESULTS

A single-base-pair transition was detected. This was a substitution of G to A of the second nucleotide position of codon 124 in the betaig-h3 gene that led to a replacement of histidine for arginine (Arg124His, CGC-->CAC). This mutation was the precise one previously reported for Avellino dystrophy. Although the proband was homozygotic for the mutant alleles, his grandmother, and parents were heterozygotic for these alleles. No sequence modification in the codon 124 from 50 nonaffected control individuals was detected. Clinical findings of the proband were severe. Keratectomies were performed for both his eyes 5 times for a 24-year period. His grandmother and parents showed mild clinical symptoms, had a few annular granules in the subepithelial stroma, and maintained good visual acuities.

CONCLUSION

Arg124His mutation of the betaig-h3 gene was found in a pedigree with granular dystrophy. This mutation was the precise one previously reported for Avellino dystrophy. This fact shows an existence of Avellino form in Japanese. Homozygotic patient for mutant gene showed severe symptoms and an early onset.

Morphology and proliferation of B16 melanoma cells in the presence of lanthanoid and Al3+ ions

The effects of trivalent metal ions such as lanthanoid (La3+, Ce3+, Nd3+, Sm3+, Gd3+, Er3+, Yb3+, Lu3+) and Al3+ ions on the morphological change and proliferation of B16 melanoma cells in culture are discussed. These metal ions induced morphological transformations and decreased growth rates at doses of 1 mM. B16 melanoma cells treated with La3+, Ce3+, Nd3+, Sm3+, and Gd3+ showed polyhedrical spreading. Elongation of axones was dependent on the metal ions. B16 melanoma cells treated with Er3+, Yb3+, Lu3+, and Al3+ showed a long slender shape. Growth rates of melanoma cells in the presence of 1 mM of metal ions (La3+, Ce3+, Nd3+, Sm3+, Gd3+, Yb3+, Al3+) were significantly lower than that of control cells. Measurements of cell cycle indicated that the metal ions arrested the transitions from G0/G1 to S state.

Contribution of cytosolic ionic and energetic milieu change to ischemia- and reperfusion-induced injury in guinea pig heart: fluorometry and nuclear magnetic resonance studies

The contribution of cytosolic ion and energy milieu changes to ischemia/reperfusion injury was investigated in isolated guinea-pig hearts and mitochondria, with fluorometry and 31P nuclear magnetic resonance (NMR). The fura-2 Ca2+ signal during ischemia in the guinea-pig Langendorff heart changed triphasically (phases I, II, and III) and rapidly returned to the control level after the reperfusion. These triphasic changes during ischemia were affected by various agents that affect the cytosolic ion milieu: the combination of asebotoxin-III and dihydroouabain (which increase intracellular Na+) caused an increase in Ca2+ levels in the final stage (phase III) with a manifestation of contracture after the reperfusion of the heart. Inhibitors of the H+-Na+ exchange such as 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) produced a significant restorative effect on the contractility of the reperfused heart with increased proton and decreased Na+ and Ca2+ in the cytosol. The mitochondrial matrix Ca2+ ([Ca2+]m) preloaded with abnormally high Ca2+ levels was markedly increased by perfusion with either a physiologic concentration of Ca2+ or an acidified perfusate. These [Ca2+]m increases were reduced by the H+-Na+ and H+-K+ exchange inhibitor (EIPA; omeprazole), respectively. These findings will help to explain the Ca paradox at the mitochondria level (i.e., mitochondria for Ca2+ pumping play an essential role in the cellular homeostasis of Ca2+ for the maintenance of cell functions of the heart, acting like a Ca2+ scavenger in the cytosol). Factors that induce Ca2+ overload on mitochondria via sarcolemmal Ca2+ influx and any exchange mechanisms with Na+, K+, Ca2+, and H+ will lead to a loss of contractility, associated with the extremely reduced level of free energy change predicted from the reduced ATP x PCr/Pi ratio by 31P NMR.

Mindin/F-spondin family: novel ECM proteins expressed in the zebrafish embryonic axis

F-spondin is a secreted protein expressed at high levels by the floor plate cells. The C-terminal half of the protein contains six thrombospondin type 1 repeats, while the N-terminal half exhibited virtually no similarity to any other protein until recently, when a Drosophila gene termed M-spondin was cloned; its product was found to share two conserved domains with the N-terminal half of F-spondin. We report the molecular cloning of four zebrafish genes encoding secreted proteins with these conserved domains. Two are zebrafish homologs of F-spondin, while the other two, termed mindin1 and mindin2, encode mutually related novel proteins, which are more related to the Drosophila M-spondin than to F-spondin. During embryonic development, all four genes are expressed in the floor plate cells. In addition to the floor plate, mindin1 is expressed in the hypochord cells, while mindin2 is expressed in the sclerotome cells. When ectopically expressed, Mindin proteins selectively accumulate in the basal lamina, suggesting that Mindins are extracellular matrix (ECM) proteins with high affinity to the basal lamina. We also report the spatial distribution of one of the F-spondin proteins, F-spondin2. F-spondin2 is localized to the thread-like structure in the central canal of the spinal cord, which is likely to correspond to Reissner's fiber known to be present in the vertebrate phylum. In summary, our study has defined a novel gene family of ECM molecules in the vertebrate, all of which may potentially be involved in development of the midline structure.

High-frequency generation of transgenic zebrafish which reliably express GFP in whole muscles or the whole body by using promoters of zebrafish origin

Despite a number of reports on transgenic zebrafish, there have been no reports on transgenic zebrafish in which the gene is under the control of a promoter of zebrafish origin. Neither have there been reports on transgenic zebrafish in which the gene is under the control of a tissue-specific promoter/enhancer. To investigate whether it is possible to generate transgenic zebrafish which reliably express a reporter gene in specific tissues, we have isolated a zebrafish muscle-specific actin (alpha-actin) promoter and generated transgenic zebrafish in which the green fluorescent protein (GFP) reporter gene was driven by this promoter. In total, 41 GFP-expressing transgenic lines were generated with a frequency of as high as 21% (41 of 194), and GFP was specifically expressed throughout muscle cells in virtually all of the lines (40 of 41). Nonexpressing transgenic lines were rare. This demonstrates that a tissue-specific promoter can reliably drive reporter gene expression in transgenic zebrafish in a manner identical to the control of the endogeneous expression of the gene. Levels of GFP expression varied greatly from line to line; i.e., fluorescence was very weak in some lines, while it was extremely high in others. We also isolated a zebrafish cytoskeletal beta-actin promoter and generated transgenic zebrafish using a beta-actin-GFP construct. In all of the four lines generated, GFP was expressed throughout the body like the beta-actin gene, demonstrating that consistent expression could also be achieved in this case. In the present study, we also examined the effects of factors which potentially affect the transgenic frequency or expression levels. The following results were obtained: (i) expression levels of GFP in the injected embryo were not strongly correlated to transgenic frequency; (ii) the effect of the NLS peptide (SV40 T antigen nuclear localization sequence), which has been suggested to facilitate the transfer of a transgene into embryonic nuclei, remained to be elusive; (iii) a plasmid vector sequence placed upstream of the construct might reduce the expression levels of the reporter gene.

Fertility investigations in the F1 hybrid and backcross progeny of cattle (Bos taurus) and yak (B. grunniens) in Mongolia

Investigations conducted in Mongolia into the sterility of the male khainag, an F1 hybrid animal resulting from crossing cattle (Bos taurus, 2n = 60) with yaks (B. grunniens, 2n = 60), are reported. Reduced numbers of spermatogonia appear to characterise the testicular tubules of the khainag, and despite the identical cytological appearance of the two parental karyotypes, synaptic anomalies are seen at meiotic prophase in primary spermatocytes. The female khainag is fertile and can be backcrossed to cattle or yak bulls to produce a B1 backcross animal, the ortoom. Further backcrossing of ortoom females to cattle or yaks will yield a B2 backcross animal, the usanguzee. The impression is gained of better meiotic pairing in the backcross animals than in the khainag. The "Haldane Rule" is followed perfectly by the cattle x yak hybrid; namely, sterility is confined to the male.

Plus/minus screening of rabbit corneal endothelial cDNA library

Plus/minus screening of the rabbit corneal cDNA library was performed using corneal and iris RNA as probes. Thirteen clones were isolated: three ferritin H-chains, a NADH-ubiquinone oxidoreductase B22 subunit, an alpha 1 type VIII collagen, a 25 KDa FKBP-506 binding protein (FKBP25), a thrombospondin 2, and six unknown clones. Although proteins translocated from these isolated mRNA are not corneal specific, they play an important role in the cornea. None of the isolated known mRNAs maps to chromosome 1, 16, or 20. These clones, thrombospondin excepted, were not observed in the high frequency clones in the profile of the aortic endothelial cDNA library.

Hypermethylation in the retinoblastoma gene is associated with unilateral, sporadic retinoblastoma

We previously reported 9 unilateral, sporadic retinoblastomas with hypermethylation in the 5' region of the RB gene, and we found that CpG methylation in the RB promoter inhibits the binding of the retinoblastoma binding factor 1 (RBF-1) and the activating transcription factor (ATF)-like factors, thereby resulting in a considerable reduction in RB promoter activity. In this study, we screened for hypermethylation in 121 additional cases of retinoblastoma, and found 5 tumors with hypermethylation, including 4 unilateral, sporadic tumors, and one hereditary tumor. The hereditary tumor had a germline deletion of one allele, and the hypermethylation was an acquired, epigenetic change in the other allele. Another tumor had hypermethylation restricted to approximately 800 base pairs in the RB promoter region including the essential RBF-1 and ATF sites. The frequency of hypermethylation in unilateral, sporadic tumors was 9.3% combining our previous and present examinations (13 among 140), whereas the frequency was 1.0% in bilateral hereditary tumors (one among 101). The statistical analyses using the chi-square test indicated significant correlation between hypermethylation and unilateral, sporadic tumors (p < 0.05). These results suggest that hypermethylation in the RB gene is always an acquired, epigenetic change and causes about 9% of unilateral, sporadic tumors.

[Serum and urinary magnesium during and after cardiac surgery]

To investigate the effects of cardiopulmonary bypass (CPB) on the serum magnesium (Mg) level, we observed the perioperative changes in serum and urinary Mg in 20 patients undergoing open heart surgery. The serum Mg was in the normal range (mean +/- SE, 1.98 +/- 0.04 mg.dl-1) at the induction of anesthesia, and began to fall during CPB, reaching its lowest level (1.43 +/- 0.05 mg.dl-1) on the first postoperative day, and returned to normal level on the second postoperative day. We found a good correlation between the decrease in serum Mg and increase in urinary Mg excretion, suggesting that the decrease in serum Mg level may be attributed to the increase in urinary excretion of Mg. But, compared to the increase in urinary loss of Mg, the observed decrease in serum Mg on the first operative day was not as great as expected. Furthermore, the level of serum Mg returned to normal spontaneously on the second operative day. These observations suggest that Mg was transferred from the intracellular to the extracellular compartment during and after CPB.

A hemizygous A to CC base change of the CHM gene causing choroideremia associated with pinealoma

BACKGROUND

Although mutations of the CHM gene have been reported in the Caucasian patients with choroideremia, there have been no such reports in non-Caucasian patients. We analyzed the CHM gene in a Japanese patient with choroideremia associated with pinealoma.

METHODS

The method for screening was a nonradioisotopic modification of single-strand conformation polymorphism (SSCP) analysis. The PCR products from the patient and the carrier were screened and directly sequenced using an automated DNA sequencer. The PCR product of the carrier was also subcloned into a vector and the subcloned products were sequenced.

RESULTS

SSCP analysis showed an identical abnormal band shift in the patient and the carrier. Direct sequence analysis showed a hemizygous A to CC mutation at nucleotide 1608 of the CHM gene in the patient, suspected to result in the absence or truncation of the predicted CHM protein. The sequence using both the PCR product and the subcloned DNA of the carrier showed both wild-type and mutant bands indicating a heterozygote.

CONCLUSION

The hemizygous mutation was detected in a patient and the heterozygous pattern in his mother, the carrier, suggesting that this mutation caused the disease.

The level of erythrocyte aldose reductase is associated with the severity of diabetic retinopathy

To examine whether the level of erythrocyte aldose reductase is a risk factor for the severity of diabetic retinopathy, the enzyme level in 97 non-insulin-dependent diabetes mellitus (NIDDM) patients was measured by the two-site enzyme-linked immunosorbent assay. Based on the results of fundus photography and biomicroscopy, the severity of retinopathy was classified among NIDDM patients of more than 10 years. The level of erythrocyte aldose reductase was significantly higher in the patients with active proliferative retinopathy than in those with nonproliferative or quiescent proliferative retinopathy. Multivariate logistic regression analysis demonstrated that the level of erythrocyte aldose reductase was an independent risk factor for active proliferative retinopathy (odds ratio, 1.28; 95% confidence interval, 1.01-1.61). The results suggest that a high level of erythrocyte aldose reductase in NIDDM patients may affect the prognosis of diabetic retinopathy. Patients with high enzyme levels would need to be closely followed up in the management of the retinal complication.

Immunolocalization of Drosophila eye-specific diacylgylcerol kinase, rdgA, which is essential for the maintenance of the photoreceptor

The Drosophila retinal degeneration A (rdgA) mutant has photoreceptor cells that degenerate within a week after eclosion. The degeneration starts with the disruption of the subrhabdomeric cisternae (SRC), which are the organelles essential for the transport of phospholipids to the photoreceptive membranes. Our previous biochemical and molecular studies suggested that the rdgA gene encodes an eye-specific diacylglycerol kinase (DGK). In this study, we show that retinal degeneration is prevented by the introduction of the eye-DGK gene in the rdgA mutant genome, suggesting that the DGK activity is crucial for the maintenance of the photoreceptor. Furthermore, by immunohistochemical analysis, we have demonstrated that the rdgA protein is predominantly associated with the SRC, suggesting that the conversion from diacylglycerol (DG) to phosphatidic acid (PA) most actively occurs in SRC. The analysis of the eyes of mutants homozygous for rdgA and eye-protein kinase C mutations indicates that retinal degeneration is caused by the deficiency of PA rather than excessive accumulation of DG. From these data, we conclude that the production of PA in the SRC membranes is essential for the maintenance of the photoreceptor.

Molecular cloning of a diacylglycerol kinase isozyme predominantly expressed in rat retina

We have cloned and characterized a new diacylglycerol kinase (DGK) isozyme which is expressed in the retina and the brain of rat. The cDNA contains an open reading frame of 567 amino acid residues with a predicted protein of 64 kDa and shows very high homology to human DGK epsilon. The new DGK isozyme contains two distinctive zinc-finger structures and a putative catalytic domain. This DGK expressed predominantly in the inner and outer nuclear layers of retina. This expression pattern is different from those of the previously cloned DGKs including the human DGK epsilon, suggesting that this DGK isozyme has potential importance in visual functions as was the case in Drosophila retinal cells.

Effects of ruthenium red on the cellular functions and ultrastructure in intact ferret ventricular muscles

The effects of ruthenium red (RR) on the cellular functions (intracellular Ca2+ handling and contraction) and permeation of the dye through the cell membrane were investigated in intact ferret papillary muscles. The intracellular Ca2+ concentration ([Ca2+]i), measured using aequorin, was simultaneously recorded with tension. The permeation of the dye through the cell membrane was studied with electronmicroscopy. The preparation was continuously stimulated at 0.2 Hz and treated with 50 microM RR at 30 degrees C. [Ca2+]i was increased by electrical stimulation (0.07 and 2 Hz) and rapid cooling (from 30 to 4 degrees C) (RC). In electrical stimulation, RR time-dependently decreased the peak light of aequorin without a significant change in the time course at 30 degrees C. However, in RC, treatment with RR for about 100 min significantly prolonged the decay time of the light signal and increased the peak light. The peak tension in RC was decreased after treatment with RR for a longer time. The pCa-tension relation of skinned preparations was significantly shifted to the right by 50 microM RR. In the RR (50 microM)-treated specimens, mitochondrial outer membranes were darkly stained if OsO4 was used for fixation. Even though the specimen treated with 500 microM RR was fixed without OsO4 and electron staining, the matrices of mitochondria became electron dense. We concluded that RR could penetrate into intact mammalian cardiac myocytes, and that RR inhibits the release of Ca2+ from the sarcoplasmic reticulum in electrical stimulation, inhibits mitochondrial Ca2+ uptake, and decreases the Ca2+ sensitivity of the myofilaments.

Molecular cloning and characterization of Drosophila genes encoding small GTPases of the rab and rho families

We have isolated eight genes from Drosophila, small GTPases. They can be classified into three rab family genes (Drab2, Drab5, Drab11) and five rho family genes (Drac1a, Drac1b, Drac3, Dcdc42, DrhoA). While Drac3 is a novel type of rac gene, others are homologues of known mammalian genes for small GTPases. Northern blot analyses showed that all the genes are expressed throughout all developmental stages from embryo to adult. In situ hybridization to embryos revealed that Drab2, Drac1b, and Drac3 are highly expressed in the nervous system, in the trunk mesoderm, and in the cephalic mesoderm, respectively. Since hemocytes are derived from the cephalic mesoderm, we carried out double stainings using a hemocyte marker anti-peroxidasin antibody and Drac3 in situ hybridization. We found that Drac3 is expressed in hemocyte precursor cells. In the Drac3 deficiency embryos, the hemocyte precursor cells start to differentiate normally, but never develop into mature hemocytes, indicating that Drac3 is essential for their maturation. The DrhoA and Dcdc42 genes complemented S. cerevisiae rho1 and cdc42 mutations in the same manner as human rhoA and CDC42, respectively. These results suggest functional similarity between Drosophila and mammalian small GTPase genes.