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PubMed2000

Involvement of cystatin C in oxidative stress-induced apoptosis of cultured rat CNS neurons.

Oxidative stress is involved in neuronal degeneration in cerebrovascular injury, neuropathology and aging. When rat CNS neurons were cultured in a high (50%) oxygen atmosphere, the neurons died. This high oxygen-induced cell death showed features of apoptotic cell death, characterized by DNA fragmentation, and was blocked by inhibitor of protein synthesis. We found that cystatin C and HuC mRNA, the products of which are an inhibitor of cysteine proteases and an RNA binding protein, respectively, were up-regulated in neurons cultured in the high oxygen atmosphere. In the present study, we focused on cystatin C. Cystatin C protein levels were also increased in neurons cultured in the high oxygen atmosphere. In situ hybridization with an RNA probe for rat cystatin C and immunocytochemistry with anti-human cystatin C antibody showed that microtubule-associated protein 2 (MAP2)-positive neurons expressed cystatin C mRNA and protein, respectively, in the high oxygen atmosphere. These results indicated that oxidative stress stimulates an increase in cystatin C expression in cultured neurons, and that cystatin C might have important roles in regulation of apoptosis elicited by oxidative stress.

Animals↗
PubMed1994

Evidence for the interaction of valine-10 in cystatin C with the S2 subsite of cathepsin B.

The interactions between wild-type or mutant recombinant forms of human cystatin C and rat cathepsin B were characterized by measuring progress curves for substrate hydrolysis in the presence of inhibitor. The investigation was guided by the use of computer modeling and explores the possibility that amino acid residues in the N-terminal region of cystatin C interact with substrate-binding regions in the target enzyme. With cystatin C that has Val-10 replaced by an Arg residue (Val10Arg cystatin C), the inhibition constant, K(i), increased 31-fold if the isosteric substitution Glu-245 to Gln was made in cathepsin B. When the wild-type form of the inhibitor was used, the corresponding effect on K(i) was less than 2-fold. In a similar study, using cathepsin B in which the substitution to Gln is instead at Glu-171, no such difference in how K(i) is affected was observed. Both Glu-245 and Glu-171 are located in the S2 subsite of cathepsin B. The observed effects on K(i) indicate that the additional positive charge introduced in Val10Arg cystatin C is interacting with the negative charge on Glu-245 in cathepsin B when these two proteins form a complex; the cystatin variant is thus binding in a substratelike manner with this region of the enzyme. Indirectly, these results suggest that when native cystatin C and cathepsin B form a complex, Val-10 in the inhibitor interacts with the S2 subsite of the enzyme. A K(i) value of 0.13 nM was obtained for the interaction of Val10Arg cystatin C with papain.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2002

Modulation of cystatin C expression impairs the invasive and tumorigenic potential of human glioblastoma cells.

Increases in the abundance of cathepsin B transcript and protein with increased tumor grade and changes in subcellular localization and activity of this enzyme. We observed progressive reductions in levels of the protease inhibitor cystatin C, an inhibitor of cathepsin B with corresponding increases in the malignancy of glioma cell lines, implying an inverse correlation between cystatin C and tumor grade. To investigate the role of cystatin C in the invasion of brain tumor cells, we stably transfected SNB19 glioblastoma cells with either a 0.4-kb cDNA construct of human cystatin C in the sense orientation or an empty vector. Clones expressing sense-cystatin C cDNA had higher cystatin C mRNA and protein levels than did control cells. Sense-transfected cells were also markedly less invasive than control cells in a Matrigel invasion assay and in a coculture assay of SNB19 spheroids and fetal rat brain aggregates. Finally, the sense-transfected cells did not form tumors in nude mice upon intracerebral injection. These results strongly implicate cystatin C in the invasiveness of human glioblastoma cells and suggest that sense transcripts of cystatin C may prove useful in cancer therapy.

Animals↗
PubMed1991

Human cystatin C. role of the N-terminal segment in the inhibition of human cysteine proteinases and in its inactivation by leucocyte elastase.

Leucocyte elastase in catalytic amounts was observed to rapidly cleave the Val-10-Gly-11 bond of the human cysteine-proteinase inhibitor cystatin C at neutral pH. The resulting modified inhibitor had size and amino acid composition consistent with a cystatin C molecule devoid of the N-terminal Ser-1-Val-10 decapeptide. Leucocyte-elastase-modified cystatin C had more than 240-fold lower affinity than native cystatin C for papain. Removal of the N-terminal decapeptide of human cystatin C also decreased inhibition of human cathepsins B and L by three orders of magnitude, but decreased inhibition of cathepsin H by only 5-fold. A tripeptidyldiazomethane analogue of of the N-terminal portion of cystatin C was a good inhibitor of cathepsins B and L but a poor inhibitor of cathepsin H. It therefore appears that amino acid side chains of the N-terminal segment of cystatin C bind in the substrate-binding pockets of cathepsins B and L but not in those of cathepsin H. It is argued that the N-terminal cystatin C interaction with cathepsin B is physiologically important and hence that leucocyte elastase could have a function as a regulator of extracellular cysteine-proteinase inhibitory activity at sites of inflammation.

Amino Acid Sequence↗
PubMed2002

Serum cystatin C is not a better marker of creatinine or digoxin clearance than serum creatinine.

AIMS: To assess whether cystatin C, a new serum marker of renal function, is a better index of creatinine or digoxin clearance than serum creatinine in older people. METHODS: Twenty-two volunteers over the age of 65 years (mean 73 +/- 5) were recruited from a healthy elderly volunteer database. None of the volunteers was taking digoxin or other medication known to interfere with digoxin kinetics or assay. Digoxin was infused at a dose of 7-10 microg kg(-1) and blood samples were taken over the following 48 h and assayed for serum digoxin. Serum cystatin C, creatinine and creatinine clearance were measured and a calculated creatinine clearance was estimated using the Cockcroft Gault formula. Digoxin clearance was calculated using a pharmacokinetic software package. All values were log transformed to normalize their distribution. RESULTS: Of the 22 volunteers enrolled into the study, 18 completed the study. Serum cystatin C ranged between 0.72 and 1.89 mg l(-1) and serum creatinine ranged from 69.6 to 153.9 micromol l(-1). Measured creatinine clearance ranged from 38 to 123 ml min(-1) and calculated creatinine clearance from 29.5 to 88.0 ml min(-1). Digoxin clearance ranged from 51.0 to 103.5 ml min(-1). Cystatin C correlated extremely well with creatinine (r=0.93, P<0.001, 95% CI 0.82, 0.97) and with creatinine clearance (r=0.67, P=0.002, 95% CI 0.3, 0.87). Neither serum cystatin C nor serum creatinine correlated with digoxin clearance (r=0.25, P=0.31, 95% CI -0.25, 0.64 and r=0.44, P=0.068, 95% CI -0.03, 0.75, respectively). Measured creatinine clearance, however, did correlate well with digoxin clearance (r=0.55, P=0.018, 95% CI 0.11, 0.81). CONCLUSIONS: Serum cystatin C and serum creatinine show very similar correlations with creatinine and digoxin clearances. Serum cystatin C does not offer any advantages in this respect. It remains to be seen whether cystatin C offers any advantage over creatinine in elderly people in other respects.

Aged↗
PubMed2002

Upregulation of cystatin C expression in the rat hippocampus during epileptogenesis in the amygdala stimulation model of temporal lobe epilepsy.

PURPOSE: Cystatin C is a cysteine proteinase inhibitor with widespread distribution in body fluids and tissues, abundant in the cerebrospinal fluid and in brain tissue. There is an implied role for cystatin C in several neurologic disorders, but the actual function of cystatin C in the brain remains unknown. Moreover, the reports on the distribution of cystatin C in the brain are controversial. We present the data on the distribution of cystatin C in normal brain tissue and during epileptogenesis. METHODS: Epileptogenesis was triggered by inducing self-sustained status epilepticus (SSSE) with a 20- to 30-min electrical stimulation of the amygdala in rats. Animals were monitored continuously for 2 weeks with video-EEG to ascertain that they were in an epileptogenic phase. RESULTS: Analysis of double-stained immunopreparations indicated that in normal brain, cystatin C is expressed mainly in microglia. In epileptogenic animals, immunostaining was increased in the microglia as well as in the neuropil at 4 days, 1 week, and 2 weeks after SSSE. Moreover, the density of cystatin C-positive microglia was associated with the severity of neuronal damage in the CA1 subfield of the hippocampus. CONCLUSIONS: This is the first report linking cystatin C with epileptogenesis and epilepsy. Further studies will explore the potential neuroprotective functions of this protein during epileptogenesis and whether the manipulation of its expression or function will have therapeutic implications.

Amygdala↗
PubMed2002

Serum cystatin C for assessment of glomerular filtration rate in pregnant and non-pregnant women. Indications of altered filtration process in pregnancy.

Serum cystatin C is believed to reflect the glomerular filtration rate (GFR) more closely than serum creatinine in many contexts and a reference interval for serum cystatin C in term pregnancy has been defined to enable its use also in pregnant women. However, serum cystatin C levels were not found to be decreased in term pregnancy, though GFR of low molecular mass substances is known to increase by at least 40% by the third trimester. The aim of this study was therefore to determine whether serum cystatin C is a reliable GFR marker also in pregnant women. GFR was determined by measurement of plasma clearance of iohexol in 48 previously healthy women in their third trimester and in 12 healthy nonpregnant women, and was compared with their serum levels of cystatin C and creatinine. Both serum cystatin C and creatinine levels were significantly related to GFR for both pregnant and non-pregnant women. However, the correlation between cystatin C and GFR was set at different levels for pregnant and nonpregnant women. Our results indicate a physiological difference between the filtration processes in kidneys of pregnant and non-pregnant women, whether it is size-dependent, configuration-dependent or charge-dependent. Nevertheless, serum cystatin C seems to reflect GFR reliably in both non-pregnant and pregnant, healthy and hypertensive women.

Adult↗
PubMed1998

Serum cystatin C as a marker of the renal function.

The protease inhibitor cystatin C is a non-glycosylated low molecular weight protein (Mr=13359) which is produced by all nucleated cells at a constant rate, freely filtered by the renal glomeruli, and catabolized in the tubuli. The aim of the study was to elucidate the applicability of serum cystatin C as a marker of glomerular filtration rate (GFR) in patients with various kidney diseases with a wide range of renal function and in dialysis patients. Seventy-six patients with various kidney diseases (aged 20 to 79 years) and 61 dialysis patients (aged 21 to 82 years) were included. Serum cystatin C was measured by automated particle-enhanced immunoturbidimetry, serum and urine creatinine by an enzymatic method, and GFR by 99mTc-DTPA-clearance using a single plasma sample method. Serum cystatin C in patients with various kidney diseases was 1.90+/-0.98 mg/L (mean+/-SD) and in dialysis patients 7.14+/-1.91 mg/L. In the non-dialysis patients a linear relationship was found between 99mTc-DTPA-clearance and 1/serum cystatin C (r=0.91, p-value<0.0001), 1/serum creatinine (r=0.89, p-value<0.0001), and creatinine-clearance (r=0.88, p-value<0.0001). Comparison of the non-parametric ROC plots for serum cystatin C (area under the curve (AUC)=0.9665; SE=0.0169), serum creatinine (AUC=0.9554; SE=0.0205), and creatinine-clearance (AUC=0.9731; SE=0.0160) revealed no significant differences (p-values: 0.50, 0.78, and 0.49). In conclusion, cystatin C may be a likewise good marker of the GFR as serum creatinine and creatinine-clearance, cystatin C having the advantage being independent of gender and muscle mass.

Adult↗
PubMed1999

Evaluation of the Dade Behring N Latex Cystatin C assay on the Dade Behring Nephelometer II System.

The Dade Behring N Latex Cystatin C assay, a particle-enhanced nephelometric immunoassay for measuring serum cystatin C, was evaluated on the Dade Behring Nephelometer II. The assay time was 6 min and the throughput was 75 samples per hour. The sample volume was 40 microL and the measuring range was 0.25-7.90 mg/L. Imprecision studies revealed within-run CVs < 1.8% and between-run CVs < 1.8% in the concentration range 0.87-4.63 mg/L. Recovery was 92.4-101.3%. Linearity studies showed excellent correlation between the theoretical and obtained values. No interferences were detected from haemoglobin < 1.0 mmol/ L, bilirubin <512 micromol/L and Intralipid <20 g/L. Stability of cystatin C in serum was 7 days at temperatures from 20 degrees C to 20 degrees C and 6 months at -80 degrees C. Measurements of cystatin C in heparin-plasma and EDTA-plasma did not differ significantly from cystatin C measured in serum. Fifty patient samples run on the Dade Behring Nephelometer II (y) were compared to the Dako Cystatin C assay (x). The Passing-Bablok regression analysis revealed y = 1.105x - 0.340. In conclusion, the Dade Behring N Latex Cystatin C assay was precise and correlated with the Dako Cystatin C assay.

Calibration↗
PubMed2006

Renal extraction of cystatin C vs 125I-iothalamate in hypertensive patients.

BACKGROUND: Several markers are available to estimate the glomerular filtration rate (GFR) in patients. Cystatin C is a relatively new marker and has been suggested as an alternative for creatinine. Numerous studies have been performed to evaluate the usefulness of cystatin C to estimate GFR. The aim of this study is to compare the renal extraction of cystatin C with that of 125I-iothalamate in hypertensive patients. METHODS: Forty hypertensive patients with unilateral renal artery stenosis, and who used at least two antihypertensive agents, were studied. For the determination of the renal extraction ratio, blood samples were drawn simultaneously from the renal vein and the abdominal aorta. The renal extraction ratio was calculated as ([A]-[V])/[A], in which A is the plasma concentration of the compound from the abdominal aorta, and V is the plasma concentration of the compound from the renal vein. RESULTS: The mean difference between the renal extraction ratio of cystatin C and that of 125I-iothalamate was 0.002. The 95% confidence interval (CI) for the mean difference was -0.036 to 0.032, which was not statistically significant. However, the limits of agreement were large (-0.271 and 0.267). CONCLUSIONS: Despite a lower reported glomerular sieving coefficient of cystatin C, the mean renal extraction of cystatin C was equal to the mean renal extraction of 125I-iothalamate in hypertensive patients, suggesting tubular secretion of cystatin C. Combined with the large variation in the renal extraction of cystatin C, these findings cast doubts on its usefulness as a glomerular filtration marker.

Adult↗
PubMed2006

Serum cystatin C as an endogenous marker of renal function in patients with mild to moderate impairment of kidney function.

BACKGROUND: Estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with chronic kidney disease (CKD). Recently, serum cystatin C was proposed as a new endogenous marker of GFR and in our study its diagnostic accuracy was compared with that of other markers of GFR. METHODS: In this study, 164 patients with CKD stages 2-3 (GFR 30-89 ml/min/1.73 m2), who had performed 51Cr-labelled ethylenediaminetetra-acetic acid clearance, were enrolled. In each patient, serum creatinine and serum cystatin C were determined. Creatinine clearance was calculated using the Cockcroft-Gault (C&G) and the modification of diet in renal disease (MDRD) formulas. RESULTS: The mean 51CrEDTA clearance was 57 ml/min/1.73 m2, the mean serum creatinine 149 micromol/l and the mean serum cystatin C 1.74 mg/l. We found significant correlation between 51CrEDTA clearance and serum creatinine (R = -0.666), serum cystatin C (R = -0.792), reciprocal of serum creatinine (R = 0.628), reciprocal of serum cystatin C (R = 0.753) and calculated creatinine clearance from the formulas C&G (R = 0.515) and MDRD formulas (R = 0.716). The receiver operating characteristic (ROC) curve analysis (cut-off for GFR 60 ml/min/1.73 m2) showed that serum cystatin C had a significantly higher diagnostic accuracy than serum creatinine (P = 0.04) and calculated creatinine clearance from the C&G formula (P < 0.0001), though only in female patients. No difference in diagnostic accuracy was found between serum cystatin C and creatinine clearance calculated from the MDRD formula. CONCLUSIONS: Our results indicate that serum cystatin C is a reliable marker of GFR in patients with mildly to moderately impaired kidney function and has a higher diagnostic accuracy than serum creatinine and calculated creatinine clearance from the C&G formula in female patients.

Adolescent↗
PubMed2007

Association of cystatin C and estimated GFR with inflammatory biomarkers: the Heart and Soul Study.

BACKGROUND: Cystatin C is a marker of kidney function that may also be associated with inflammation. In this study, we compared the relative strengths of association of cystatin C and estimated glomerular filtration rate (eGFR) with inflammatory biomarkers. METHODS: We measured serum cystatin C and creatinine in 990 outpatients with coronary artery disease enrolled in the Heart and Soul Study. GFR was estimated (eGFR) by the abbreviated Modification of Diet in Renal Disease (MDRD) equation. We compared the associations of serum cystatin C and eGFR with C-reactive protein (CRP) and fibrinogen, after adjustment for 24 h creatinine clearance. RESULTS: Cystatin C concentrations had moderate correlations with CRP (r=0.15, P<0.001) and fibrinogen (r=0.26, P<0.0001); eGFR had similar correlations with CRP (r=-0.17, P=0.01) and fibrinogen (r=-0.25, P<0.001) among persons with eGFR 60 ml/min (r=0.04, P=0.32; r=-0.03, P=0.38). Quartiles of cystatin C were strongly and directly associated with CRP (P=0.02) and fibrinogen (P<0.007) after multivariate adjustment. However, these associations disappeared after adjustment for creatinine clearance (P=0.26 and 0.23, respectively). CONCLUSIONS: Cystatin C concentrations have moderate associations with CRP and fibrinogen that are not independent of creatinine clearance. Although a gold standard of kidney function is lacking, this analysis suggests that cystatin C captures an association of mildly impaired kidney function with increased inflammation.

Aged↗
PubMed1999

Inhibition of B16 melanoma metastasis by overexpression of the cysteine proteinase inhibitor cystatin C.

Progression to metastasis has been correlated with increased cysteine proteinase activity for a number of tumour types. One mechanism of cysteine proteinase regulation in normal cells is by natural protease inhibitors, the cystatins. Here we further characterize a transfected cell line showing increased cystatin C transcription driven by cytomegalovirus (CMV) promoter/enhancer sequences. Properties of this cystatin C altered cell line such as growth in vitro, lung colonization after tail vein injection in mice, production of cystatin, and cysteine proteinase inhibitor activities were examined. Although there was no difference between the growth rate of the cystatin transfected cell line and that of the control, there was a substantial difference in metastatic ability. No increase was noted in cystatin C secretion into the media for the cystatin C transfected cell line compared with the control transfected cell line. There was, however, a difference in cysteine protease inhibitor activity in the cell-free extracts. These results show that alteration of cystatin C levels by overexpression in B16 melanoma alters properties associated with metastasis.

Animals↗
PubMed2003

Measuring glomerular filtration rate with cystatin C and beta-trace protein in children with spina bifida.

PURPOSE: We compared the diagnostic performance of cystatin C and beta-trace protein with serum creatinine and the Schwartz formula for the estimation of glomerular filtration rate in children with spina bifida. MATERIALS AND METHODS: Cystatin C, beta-trace protein and serum creatinine in children who underwent routine measurement of glomerular filtration rate were obtained in a prospective study. A spina bifida group (27 measurements in 27 patients 1.4 to 20.0 years old, 15 female, 12 male) was compared with a group of controls (211 measurements in 201 patients with various other renal pathologies 1.0 to 20.2 years old, 89 female, 122 male). All patients underwent nuclear medicine clearance investigations with 99mtechnetium diethylenetetraminepentaacetic acid. Z scores were calculated for body mass index, height and weight. Receiver operating characteristic (ROC) analysis and ROC plots were done to assess their diagnostic accuracy. RESULTS: Serum creatinine and the Schwartz formula did not correlate with glomerular filtration rate in the patients with spina bifida. Correlation coefficients for cystatin C were 0.45 and 0.84 in the spina bifida and control groups, respectively, while correlation coefficients for beta-trace protein were 0.31 and 0.75, respectively. For both groups ROC area was highest for cystatin C (up to 0.97 ROC area in control group). CONCLUSIONS: Only cystatin C served as a suitable marker to estimate glomerular filtration rate in patients with spina bifida. Cystatin C proved to be a superior marker in patients with spina bifida. In the control group the Schwartz formula was comparable to cystatin C and beta-trace protein, although cystatin C remained superior.

Adolescent↗
PubMed1996

Isolation and characterization of the mouse cystatin B gene.

The cystatins make up a large superfamily of proteins that inhibit cysteine proteases. Recently, we showed that loss-of-function mutations in the human cystatin B gene are responsible for progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1). However, despite the known role of cystatin B in cysteine protease inhibition, it is not clear why decreased levels of this protein cause EPM1. To provide new insights into the biochemical and pathological mechanisms of EPM1, we are working toward developing an animal model for this disease. Here we present the mouse cystatin B nucleotide and amino acid sequence. We show that the mouse gene spans a 3-kb genomic region and contains 3 exons and 2 introns, identical to the structure of both the rat and human cystatin B genes. The amino acid sequence identity of the protein is 86%, 79%, and 71% to that of the rat, human, and bovine cystatin B proteins, respectively. In addition, we show that the mouse cystatin B gene is expressed in many tissues, similar to results observed previously in humans. Finally, we report the mapping of the mouse cystatin B gene (Stfb) to chromosome 10, further extending the synteny between this region of the mouse chromosome and human chromosome 21q22.3.

Amino Acid Sequence↗
PubMed1995

Transthyretin and cystatin C are catabolized in proximal tubular epithelial cells and the proteins are not useful as markers for renal cell carcinomas.

Ten human kidney specimens and thirty-two renal cell carcinomas were investigated for the presence of transthyretin mRNA and cystatin C mRNA using Northern blot analysis. Five of ten kidney specimens and 15 of 32 renal carcinomas were also immunohistochemically investigated for the presence of the corresponding proteins. Transthyretin mRNA could not be detected in any of the normal or neoplastic tissue preparations, whereas low amounts of cystatin C mRNA were found in nine of ten normal kidneys and in 24 of 32 renal cell carcinomas. Immunoreactive transthyretin and cystatin C were present in proximal tubular epithelial cells of all kidney specimens, whereas neither of the proteins was detected the tumour cells of the renal carcinomas. Immunoreactive cystatin C was, however, demonstrated in scattered monocyte/macrophage-like cells. We conclude that the presence of immunoreactive transthyretin and cystatin C in proximal tubular cells of the kidney is most likely due to reabsorption of the proteins from the primary urine. The small amounts of cystatin C mRNA in some of the normal and neoplastic renal preparations are probably due to cystatin C synthesis in macrophages. Transthyretin has been recommended as an immunohistochemical marker for renal cell carcinomas. Our results, however, clearly indicate that neither transthyretin nor cystatin C constitutes a useful marker for such neoplasms.

Biomarkers, Tumor↗
PubMed1999

Functional aspects of the human salivary cystatins in the oral environment.

OBJECTIVES: The aim of this study was to investigate the cysteine protease inhibitory properties of the human salivary cystatins S, SA and SN in order to identify potential in vivo target cysteine proteases which may include those involved in periodontal tissue destruction. In addition, the potential role of the salivary cystatins with respect to the tooth mineral balance and pellicle formation was also investigated. METHODS: Salivary cystatins S major, S minor, SA, SAT (a truncated form of SA) and SN were purified from human submandibular sublingual saliva. Sensitive fluorometric assays were used to test the inhibitory action of each purified form of salivary cystatin against a variety of cysteine proteases and to determine whether pH affected their inhibitory activity towards the well-characterized cysteine protease papain. Their potential role in the mineral balance of the tooth was assessed by the measurement of calcium binding and the rate of binding to carbonated apatite (CAP). RESULTS AND CONCLUSIONS: Salivary cystatin SN was found to inhibit the human lysosomal cathepsins B, H and L and salivary cystatin SA was found to inhibit human lysosomal cathepsin L in vitro. These proteases are involved in periodontal tissue destruction and these data suggest that salivary cystatins SA and SN are involved in the control of the proteolytic events in vivo. Salivary cystatin S was not an inhibitor of the cysteine proteases tested suggesting that its primary role is not as a cysteine protease inhibitor. However, S was able to bind more calcium and bind more rapidly to CAP than SA or SN, suggesting that its primary role in the oral environment is likely to be the involvement with the mineral balance of the tooth.

Amino Acid Sequence↗
PubMed1992

Strong conservation of the expression of cystatin C gene in choroid plexus.

The expression of the cystatin C gene was studied by Northern analysis of RNA isolated from the choroid plexus, other brain tissues, and liver from 11 mammalian and 4 avian species. The probe used for hybridization was cystatin C cDNA isolated previously from a rat choroid plexus cDNA library. Strong conservation of the expression of the cystatin C gene in choroid plexus was suggested by the observation of substantial levels of cystatin C mRNA in choroid plexus RNA from all mammalian and avian species studied. In contrast, levels of cystatin C mRNA in total liver RNA varied widely for mammalian as well as for avian species. It was concluded that the synthesis of cystatin C in choroid plexus has probably been conserved since the stage of the stem reptiles, the common ancestors of mammals and birds. The cystatin C gene was also found to be expressed early in ontogeny, as indicated by the observation of similar cystatin C mRNA levels in choroid plexus RNA from newly hatched and adult chickens.

Animals↗