The effect of trauma on neutrophil L-selectin expression and sL-selectin serum levels

Among identified adhesion molecules, the L-selectin on neutrophils enables the first step of leukocyte adherence to activated endothelial cells. To allow firm adhesion of neutrophils, L-selectin is then split off the cell membrane. It was hypothetized that an increase of the constitutively high serum level of soluble L-selectin may indicate an ongoing pathological neutrophil sequestration to the endothelial cells associated with activation and injury of the cells. To evaluate this hypothesis, sL-selectin serum levels and neutrophil L-selectin expression of healthy volunteers (group A, n = 15), as well as of surgical patients, were investigated. Group B (n = 26) included patients subjected to elective limb surgery (mean operation time, 122 min), and group C (n = 45) comprised trauma patients. sL-selectin serum levels were measured daily over a 14-day period. Neutrophil L-selectin expression was evaluated by FACS analysis using the humanized anti-L-selectin antibody HuDreg 55 over a period of 3 days at minimum in both experimental groups. The binding of sL-selectin to endothelial cells was also examined in vitro. Elective limb surgery resulted in lower pre- and post-operative sL-selectin plasma levels (800-1,000 ng/mL) compared to healthy volunteers (1,100-1,200 ng/mL) with insignificant changes throughout the study period. Trauma patients revealed even lower sL-selectin levels (400-600 ng/mL). When these patients were discriminated by the multiple organ dysfunction (MOD) score of Moore in +MOD (n = 9, ISS = 31.7) and -MOD (n = 36, ISS = 25.0), a significant difference became evident. In +MOD patients sL-selectin levels remained on a low basis of 350 ng/mL, whereas in -MOD patients the initial low sL-selectin level subsequently rose to 800 ng/mL, similar to that of elective surgery patients. FACS analysis revealed a significant drop in neutrophil L-selectin expression 24 h after trauma compared to normal. Also, +MOD and -MOD patients were significantly discriminated by the L-selectin expression at this time. The in vitro studies revealed evidence for binding of sL-selectin to endothelial cells independently on the presence of neutrophils. According to our data, increasing severity of the post-operative/posttraumatic course is associated with decreasing sL-selectin serum levels and also reduced neutrophil L-selectin expression. In view of the in vitro results, this probably indicates competitive enhanced binding of sL-selectin to endothelial cells, thus masking the elevated activation of neutrophils and their ability for endothelial adherence.

Use of a myocutaneous flap after resection of a large lymphangioma

We report on an 11-year-old girl with a large lymphangioma involving the lower third of the abdominal wall, the mons pubis, both labia majora, the perianal region and extending into the pelvic bones. Because of an increasing lymphorrhea from the cutaneous lesions resulting in considerable discomfort and skin infections, the patient sought medical advice. After lymphological check-up excluded the existence of a chylous reflux, the patient was presented at a multidisciplinary medical council. A palliative surgical treatment was recommended consisting of the resection of the most affected suprapubic region and the coverage of the resulting tissue defect with a gracilis myocutaneous flap. Postoperatively, a venous stasis at the tip of the skin paddle developed, which was relieved by the use of leeches and required secondary closure. Despite these complications, the surgical intervention yielded an acceptable cosmetic result, a diminution of lymphorrhea and hence subjectively some relief.

CONCLUSION

Due to the variability of lymphangiomas, an assessment by a multidisciplinary consultation is proposed. With respect to therapy, the use of a myocutaneous flap represents one of the therapeutic options for large cutaneous lymphangiomas.

Evidence for further genetic heterogeneity in nephronophthisis

BACKGROUND

A new type of nephronophthisis (NPH) has been recently identified in a large Venezuelan kindred: adolescent nephronophthisis (NPH3) causes end-stage renal disease (ESRD) at a median age of 19 years. The responsible gene (NPHP3) maps to 3q21-q22. NPH3 shares with juvenile nephronophthisis (NPH1) the same disease manifestations such as polyuria, polydipsia, and secondary enuresis. Histopathological findings consist of tubular basement membrane changes, cysts at the corticomedullary junction, and a chronic sclerosing tubulointerstitial nephropathy. The only difference is a younger age at ESRD in NPH1 (median age of 13 years) when compared with NPH3.

METHODS

In order to evaluate whether there might be a fourth locus of isolated nephronophthisis, we studied eight NPH families without extrarenal disease manifestations and without linkage to the NPH1 locus (NPHP1) on chromosome 2q12-q13. ESRD was reached at ages ranging from 7 to 33 years. Individuals were haplotyped with microsatellites covering the genetic locus of NPHP3. Infantile NPH (NPH2) was excluded in all families by the clinical history and histological findings.

RESULTS

In four of the examined families haplotype analysis was compatible with linkage to the NPHP3 locus. In one of these families identity by descent was observed. In contrast, in another four families linkage was excluded for NPHP3.

CONCLUSION

Four NPH-families were neither linked to NPHP1 nor to NPHP3, indicating further genetic heterogeneity within the group of nephronophthisis. The finding of further genetic heterogeneity in NPH has important implications for genetic counselling.

Refinement of the gene locus for autosomal dominant medullary cystic kidney disease type 1 (MCKD1) and construction of a physical and partial transcriptional map of the region

Autosomal dominant medullary cystic kidney disease (MCKD) is an adult onset tubulointerstitial nephropathy that leads to salt wasting and end-stage renal failure. A gene locus (MCKD1) has been mapped on chromosome 1q21. Here we report on a large MCKD1 family of British origin linked to the MCKD1 locus. Haplotype analysis performed with markers spanning the previously reported critical MCKD1 region allowed for the refinement of this interval to 4 cM by definition of D1S305 as a new proximal flanking marker. Furthermore, we constructed a yeast artificial chromosome, P1-related artificial chromosome, and bacterial artificial chromosome contig of this region, which is only sparsely covered by the Human Genome Sequencing Project. This enabled us to map numerous expressed sequence tags within the critical interval. This physical and partial transcriptional map of the MCKD1 region is a powerful tool for the identification of positional and functional candidate genes for MCKD1 and will help to identify the disease-causing gene.

Establishing an algorithm for molecular genetic diagnostics in 127 families with juvenile nephronophthisis

BACKGROUND

Juvenile nephronophthisis (NPH1), an autosomal recessive cystic disease of the kidney, represents the most common genetic cause of end-stage renal disease in the first two decades of life. On the basis of identification of the gene (NPHP1) defective in NPH1 and the presence of homozygous deletions of NPHP1 in the majority of NPH1 patients, molecular genetic diagnosis for NPH1 is now possible. Molecular genetic testing offers the only method for definite diagnosis of NPH1 and avoids invasive diagnostic measures like renal biopsy.

METHODS

We examined 127 families (204 patients) with the presumed diagnosis of NPH using molecular genetic diagnostic techniques. In 68 families, renal biopsy was performed and was consistent with NPH, and in 61 families, there was more than one affected child ("multiplex families").

RESULTS

In 74 families (115 patients), there was proof of the diagnosis of NPH1 by detection of a homozygous deletion of the NPHP1 gene, and in 5 families a heterozygous deletion in combination with a point mutation in NPHP1 was demonstrated. Furthermore, for 16 families, NPH1 was excluded with high likelihood by linkage analysis, and for 20 families by detection of heterozygosity for two newly identified polymorphic markers within the deletion region. In 5 of the remaining 12 families, which were noninformative for these markers, fluorescence in situ hybridization did not detect any further heterozygous deletions.

CONCLUSIONS

The diagnosis of NPH1 was proven by molecular genetic techniques in 62% of families with one or more children with the presumed diagnosis of NPH. We present evidence that there is a fourth locus for NPH, since only 6 of the 26 multiplex families in whom the diagnosis of NPH1 was excluded were compatible with linkage to other loci for NPH. On the basis of the presented data, we propose an algorithm for molecular genetic diagnostics in NPH.

New insights: nephronophthisis-medullary cystic kidney disease

Nephronophthisis (NPH) and medullary cystic kidney disease (MCKD) constitute a group of renal cystic diseases, which share a common characteristic renal histologic triad of tubular basement membrane disintegration, tubular atrophy with cyst development, and interstitial cell infiltration with fibrosis. The different disease variants lead to chronic renal failure with onset at characteristic age ranges for recessive NPH and dominant MCKD. There is extensive gene locus heterogeneity with at least three different loci for nephronophthisis (NPHP1, NPHP2, and NPHP3) and two different loci for MCKD (MCKD1 and MCKD2). Juvenile nephronophthisis, in addition, can be associated with extrarenal organ involvement. We have identified by positional cloning the gene (NPHP1) for juvenile nephronophthisis (NPH1), as a first step towards understanding the pathogenesis of this disease group. Its gene product, nephrocystin, is a novel protein, which contains a src-homology 3 (SH3) domain. We put forward a hypothesis that the pathogenesis of NPH might be related to signaling processes at focal adhesions (the contact points between cells and extracellular matrix) and/or adherens junctions (the contact points between cells).

Homozygosity mapping of a gene locus for primary ciliary dyskinesia on chromosome 5p and identification of the heavy dynein chain DNAH5 as a candidate gene

Reduced mucociliary clearance in primary ciliary dyskinesia (PCD) causes recurrent infections of the upper and lower respiratory tract. The disease is usually inherited as an autosomal recessive trait. To identify a gene locus for PCD, we studied a large consanguineous family of Arabic origin. Direct examination of the respiratory cilia revealed ciliary akinesia. Electron microscopic examination of cilia showed absence of the outer dynein arms. Two of four affected individuals exhibited a situs inversus, typical for Kartagener syndrome, due to randomization of the left/right body axis. A total genome scan with 340 highly polymorphic microsatellites was performed. We localized a new gene locus for PCD to a region of homozygosity by descent on chromosome 5p15-p14 with a parametric multipoint logarithm of odds ratio (LOD) score of Zmax = 3.51 flanked by markers D5S2095 and D5S502 within an interval of 20 centimorgans sex-averaged genetic distance. Applying a polymerase chain reaction-based approach, we identified a 1.5-kb partial complementary DNA of DNAH5 encoding a Chlamydomonas-related axonemal heavy dynein chain within the critical disease interval of this new PCD locus. On the basis of the Chlamydomonas model for PCD, this gene represents an excellent candidate for PCD.

A Bartter's syndrome mutation of ROMK1 exerts dominant negative effects on K(+) conductance

Mutations in the gene encoding the renal epithelial K(+) channel ROMK1 (Kir 1.1) is one of the causes for Bartter's syndrome, an autosomal recessive disease. It results in defective renal tubular transport in the thick ascending limb of the loop of Henle that leads to hypokalemic metabolic alkalosis and loss of salt. Two novel ROMK1 mutations, L220F/A156V, have been described recently in a compound heterozygote patient demonstrating typical manifestations of Bartter's syndrome. Functional properties of these ROMK1 mutants were studied by coexpressing in Xenopus oocytes and by means of double electrode voltage clamp experiments. When both ROMK1 mutants were coexpressed no K(+) conductance could be detected. The same was found in oocytes expressing A156V-ROMK1 only or coexpressing wild type (wt) ROMK1 together with A156V-ROMK1. In contrast, K(+) conductances were indistinguishable from that of wt-ROMK1 when L220F-ROMK1 was expressed alone. Activation of protein kinase C signaling inhibited the conductance in both L220F-ROMK1 and wt-ROMK1 expressing oocytes. These effects were not seen in A156V-ROMK1 expressing oocytes. Because no further abnormalities in the properties or regulation of L220F-ROMK1 were detected, we conclude that A156V-ROMK1 has a dominant negative effect on L220F-ROMK1 thereby causing Bartter's syndrome type two in this patient.

A deletion distinct from the classical homologous recombination of juvenile nephronophthisis type 1 (NPH1) allows exact molecular definition of deletion breakpoints

Juvenile nephronophthisis, an autosomal recessive cystic kidney disease, is the most common genetic cause of end-stage renal disease in children and young adults. We recently identified by positional cloning the causative gene, NPHP1. Its gene product nephrocystin may play a role in focal adhesion and adherens junction signaling. Approximately 80% of all patients with NPH1 carry large homozygous deletions, which contain the NPHP1 gene. These common deletions are positioned within a complex arrangement of large inverted and direct repeats, suggesting unequal recombination as a potential cause for their origin. In this study we have characterized the deletion breakpoints in a family with juvenile nephronophthisis that bears a unique maternal deletion of the NPHP1 gene, which is not the result of an event of homologous recombination. We molecularly characterized the centromeric and telomeric deletion breakpoints by extensive genomic sequencing, Southern blot analysis, and cloning and sequencing of the junction fragment. We were able to exactly localize the breakpoints at the position of two guanines. The centromeric breakpoint was positioned within intron 2 of the NPHP1 gene 360 bp downstream of the 5' end of a complete LINE-1 element. Multiple topoisomerase I and II consensus sequences were found at the breakpoint sites, suggesting the involvement of topoisomerase II in the deletion mechanism. These findings provide the first data on a potential mechanism for a deletion of the NPHP1 gene, that most likely is not the result of an event of homologous recombination and thereby distinct from the known common deletions.

Molecular cloning of the critical region for glomerulopathy with fibronectin deposits (GFND) and evaluation of candidate genes

Glomerulopathy with fibronectin deposits (GFND, MIM 601894) is an autosomal dominant kidney disease that leads to terminal renal failure at a median age of 47 years. It represents a distinct entity of membranoproliferative glomerulonephritis (MPGN) type III and is characterized by the unique feature of massive glomerular deposits of fibronectin. We have recently localized a gene locus for GFND to human chromosome 1q32 by total genome linkage analysis in a large kindred, within a 4.1-cM critical interval between markers D1S2872 and D1S2891. This interval contains a cluster of genes for "regulators of complement activation" (RCA), which represent strong candidates for GFND. To identify positional candidate genes for GFND within the critical genetic interval, we here report the cloning of the entire critical GFND region in a complete YAC and partial PAC contig. We constructed a high-resolution transcriptional map, thereby defining positional and functional candidate genes for the disease. To evaluate their role in GFND, we performed functional studies on RCA proteins in GFND patients from the large kindred, as well as mutational analysis of the genes for complement receptor-2 (CR2), membrane cofactor protein (MCP), and decay accelerating factor (DAF). Although no loss-of-function mutation has been identified as yet, these data provide a basis for the examination of candidate genes for GFND and other genes for MPGN, which localize to the vicinity of the GFND region.

mut0 methylmalonic acidemia: eleven novel mutations of the methylmalonyl CoA mutase including a deletion-insertion mutation

Methylmalonic aciduria (MMA) is an autosomal-recessive disorder caused by inadequate function of methylmalonyl-CoA mutase (MCM), a nuclear-encoded, mitochondrial enzyme that uses adenosylcobalamin as a cofactor. Biochemical cell studies have delineated phenotypic variants: mut(0) phenotypes in which there is no detectable enzymatic activity and mut- phenotypes in which there is residual cobalamin-dependent activity. Mutation screening in MMA has led to the detection of 30 disease-specific mutations. In 14 patients with the mut(0) phenotype we found 11 novel mutations (K54X, A137V, F174S, 620insA, G203R, Q218H, A535P, H627R, 2085delG and 2270del4/ins5), 6 of them homozygous, consisting of 1 nonsense, 6 missense, 1 splice site, and 3 frame shift mutations. The position in relation to different functional domains in MCM allow for an interpretation of the identified mutations. Hum Mutat 16:179, 2000.

Antenatal Bartter syndrome with sensorineural deafness: refinement of the locus on chromosome 1p31

BACKGROUND

Recently a locus for antenatal Bartter syndrome associated with sensorineural deafness was mapped to human chromosome 1p31 in a single consanguineous Bedouin family (Brennan et al. Am J Hum Genet 1998; 62: 355-361).

METHODS

By haplotype analysis we demonstrate linkage to this locus in nine consanguineous families with antenatal Bartter syndrome associated with sensorineural deafness.

RESULTS

The critical interval compatible with linkage was refined to 4.0 cM by two novel recombinational events with markers D1S2661 and D1S475.

CONCLUSION

We thereby confirmed this gene locus and distinguished this clinical subtype from other variants of Bartter syndrome as a new disease entity.

Evidence of further genetic heterogeneity in autosomal dominant medullary cystic kidney disease

BACKGROUND

Autosomal dominant medullary cystic kidney disease is a genetically heterogeneous nephropathy with clinical and morphological features similar to recessively inherited juvenile nephronophthisis. Recently, a second gene locus on chromosome 16p12, MCKD2 has been mapped [1] in addition to the known locus on chromosome 1q21 (MCKD1) [2]. In a previous study we have excluded linkage for three caucasian families to the MCKD1 locus [3].

METHODS

Haplotype analysis was performed on 72 individuals (including 24 affected subjects), using a set of seven microsatellite markers spanning the critical region on chromosome 16p12-p13 of about 10.5 cM.

RESULTS

We report on haplotype analysis of closely linked markers to the MCKD2 locus in the previously studied families and two additional families.

CONCLUSION

In all five families the association of MCKD2 with the disease was excluded by a multipoint LOD score <-2, thus suggesting the involvement of a third MCKD locus.

Children with ocular motor apraxia type Cogan carry deletions in the gene (NPHP1) for juvenile nephronophthisis

Congenital ocular motor apraxia type Cogan is characterized by impairment of horizontal voluntary eye movements, ocular attraction movements, and optokinetic nystagmus. Two patients with congenital ocular motor apraxia type Cogan exhibited a newly recognized association with nephronophthisis type 1, an autosomal recessive kidney disease. Both patients possess large deletions of the NPHP1 gene. The deletion occurred on both chromosomes 2q13 in one patient and heterozygously in combination with a point mutation of the NPHP1 gene in the other. The findings will help to elucidate the pathogenetic processes involved.

Appearance of autosomal recessive polycystic kidney disease in magnetic resonance imaging and RARE-MR-urography

PURPOSE

To describe the appearance of autosomal recessive polycystic kidney disease (ARPKD) on MRI and RARE-MR urography.

MATERIALS AND METHODS

Seven boys and one girl (aged 3 months to 14 years, median 2.5 years) were evaluated. Images were obtained with 0.23-T and 1.5-T MR systems using T1-weighted (T1-W) spin-echo, T2-weighted (T2-W) turbo-spin-echo and RARE-MR-urography sequences. Signal intensities, morphological appearance of the affected kidneys and, specifically, the picture of the urinary tract on RARE-MR-urography were evaluated.

RESULTS

All children showed kidney enlargement, reniform but humpy kidney shape, homogeneously grainy renal parenchyma, normal renal pelvis and normal calyces. Signal intensity was hyperintense in T2-W images in all cases. In six cases (n = 7), T1-W images were hypointense. On RARE-MR urography a hyperintense, linear radial pattern was seen in the cortex and medulla which represents the characteristic microcystic dilatation of collecting ducts in ARPKD. Three boys and the girl presented with a few circumscribed small subcapsular cysts.

CONCLUSIONS

In order to confirm the diagnosis of ARPKD, RARE-MR urography seems to be a non-invasive imaging tool that shows directly the microcystic dilated water-filled collecting ducts.

Adenosine-triphosphate in trauma-related and elective hypothermia

BACKGROUND

In trauma patients, hypothermia is a frequent event. According to the literature, the majority of trauma patients are presenting a core temperature of less than 34 degrees C at admission. In contrast to the benefit of hypothermia in elective surgery, clinical experience with hypothermia in trauma patients has identified hypothermia to be one major cause of severe posttraumatic complications. It was hypothesized that this diverse effect of hypothermia is related to depletion of high-energy phosphates like adenosine triphosphate (ATP) in trauma patients. To verify this hypothesis, the relation of ATP plasma levels and hypothermia was examined in a clinical study.

METHODS

Three different groups of patients were under study. The first group (group A, normothermic control group) included patients (n = 15) undergoing elective surgery of the lower limb with a mean operation time of 113 minutes. The second study group (group B, hypothermic control) was composed of patients (n = 15) who were subjected to elective coronary artery bypass operation under hypothermia (31 degrees C for 48 minutes, mean total operation time being 205 minutes). The third study group (group C) included trauma patients (n = 23, mean Injury Severity Score [ISS] of 24.7). At the time of admission, 10 patients presented a core temperature more than or equal to 34 degrees C (group C1, mean ISS, 25.2; mean T(A), 34.5 degrees C), 13 patients presented a T(A) less than 34 degrees C (group C2, mean ISS, 26.0; mean T(A), 32.9 degrees C). In both groups of surgical patients, the ATP plasma level was measured preoperatively, at 2, 4, and 24 hours postoperatively. For trauma patients, this measurement was performed at admission and 24 hours later. Within the same schedule, body core temperature was recorded and the clinical course was documented as well.

RESULTS

Elective limb surgery in normothermic patients resulted only in a transient decrease in ATP plasma levels (preoperative, 87.8 micromol/dL; 4 hours postoperative, 52.0 micromol/dL). At 24 hours, the ATP plasma level (62.6 +/- 10.0 micromol/dL) has increased toward baseline level. Elective hypothermia in patients subjected to coronary bypass also resulted only in a transient decrease in ATP plasma levels. During the operation period, including hypothermia, the ATP plasma level was comparable (50.4 micromol/dL) to group A and also returned back toward normal values at 24 hours (58.2 micromol/dL). All trauma patients revealed a significant low ATP plasma level at admission compared with both control groups. Looking at subdivided groups the most significant drop in ATP plasma level (28.5 micromol/dL) was noted in patients presenting an initial core temperature less than 34 degrees C and ISS more than 30. Even 24 hours later, the ATP level of this subgroup was significantly diminished, despite a rise up to 44.4 micromol/dL. In contrast, only a moderate drop in ATP plasma concentration (59.2 micromol/dL) was noted in the group of T(A) more than or equal to 34 degrees C and ISS less than 20. This group revealed almost normal values (68.3 micromol/dL) 24 hours after trauma. In addition to hypothermia, the metabolic state, reflected by the plasma lactate levels, significantly influenced the ATP plasma levels, as high lactate levels were paralleled by low ATP levels. Also, the overall outcome was related to injury severity and hypothermia.

CONCLUSION

Hypothermia in elective surgery, established by active cooling, preserves the ATP storage and maintains an aerobic metabolism, which both contribute to the beneficial effect of hypothermia in ischemia/reperfusion in cardiovascular surgery. However, in trauma patients hypothermia is caused by insufficient heat production due to utilization of ATP under anaerobic metabolic conditions. Low ATP plasma levels combined with hypothermia seem to be a predisposition for post-traumatic complications like organ failure.

Exclusion of the candidate genes ACE and Bcl-2 for six families with nephronophthisis not linked to the NPH1 locus

BACKGROUND

Nephronophthisis (NPH) is an autosomal recessively transmitted kidney disease, characterized by cyst formation at the cortico-medullary junction, and a sclerosing tubulointerstitial nephropathy. Juvenile nephronophthisis (NPH1) is the most common genetic cause of renal failure in children and maps to chromosome 2q12-q13. The responsible gene NPHP1 has been identified and encodes for nephrocystin. Not all families with NPH demonstrate linkage to that locus.

METHODS

We studied six families with NPH without linkage to the NPH1 locus. In order to attempt identification of a new causative gene, the candidate genes ACE (angiotensin converting enzyme) and Bcl-2 (B cell leukaemia/lymphoma 2 gene) originating from mouse models, were examined. For the six families highly polymorphic microsatellites covering the whole candidate gene regions were haplotyped and linkage analysis was performed.

RESULTS

Haplotype analyses of all families examined were incompatible with linkage of the disease status to ACE or Bcl-2. Linkage analysis excluded both candidate gene regions with a LOD-score of < -2.

CONCLUSIONS

This study excluded the candidate genes ACE and Bcl-2 for NPH. Additional linkage studies need to be performed in order to identify further genes responsible for nephronophthisis.

Rare-MR-urography--a new diagnostic method in autosomal recessive polycystic kidney disease

PURPOSE

To describe the appearance of autosomal recessive polycystic kidney disease (ARPKD) by using a new diagnostic method: RARE-MR-urography.

MATERIAL AND METHODS

Eight children were evaluated using MR images from 0.23 T and 1.5 T MR units, using T1-weighted spin-echo and T2-weighted turbo spin-echo sequences and RARE-MR-urography. Signal intensities, morphological appearance of the affected kidneys and, specifically, the picture of the urinary tract in RARE-MR-urography, were evaluated.

RESULTS

All children showed enlargement, reniform but humpy kidney shape, homogeneous-grainy renal parenchyma, normal renal pelvis and calyces. Although ARPKD is always associated with some degree of congenital hepatic fibrosis, there was no bile duct dilatation or liver fibrosis at the time of examination. Signal intensity was hyperintense in T2-weighted images in all cases. In 5 cases, T1-weighted images were hypointense. In RARE-MR-urography, hyperintense, linear, radial patterns in cortex and medulla were seen, which represent microcystic dilatation of collecting ducts and are therefore characteristic of ARPKD. Four patients presented with a few circumscribed small subcapsular cysts.

CONCLUSION

RARE-MR-urography is a noninvasive method which demonstrates the pathognomonic water-filled cystic structures throughout the kindeys in ARPKD.

Renal cystic disease

Renal cystic diseases constitute the most common genetic cause for end-stage renal disease in children and young adults. Recently, there has been rapid progress regarding the identification or chromosomal localization of some of the responsible disease genes. Studies of the respective gene products and of related animal models have led to new insights into the pathophysiology of these disorders. In this review, very recent developments are discussed as they pertain to molecular genetic diagnosis, the understanding of pathophysiology, and potential novel therapeutic approaches to renal cystic diseases.

Hereditary isolated renal magnesium loss maps to chromosome 11q23

Hypomagnesemia due to isolated renal magnesium loss has previously been demonstrated in two presumably unrelated Dutch families with autosomal dominant mode of inheritance. Patients with magnesium deficiency may suffer from tetany and convulsions, but the patients with hereditary renal magnesium wasting can also be clinically nonsymptomatic. In a genomewide linkage study, we first excluded a possible candidate region, on chromosome 9q, that encompasses the gene for intestinal hypomagnesemia with secondary hypocalcemia and, subsequently, found linkage to markers on chromosome 11q23. Detailed haplotype analyses identified a common haplotype segregating in both families, suggesting both their relationship through a common ancestor and the existence of a single, hypomagnesemia-causing mutation within them. The maximum two-point LOD score (Zmax) was found for marker D11S4127 (Zmax=6.41 at a recombination fraction of. 00), whereas a multipoint analysis gave a Zmax of 8.24 between markers D11S4142 and D11S4171. Key recombination events define a 5. 6-cM region between these two markers on chromosome 11q23. We conclude that this region encompasses a gene, involved in renal magnesium handling, that is mutated in our patients and is different from the gene involved in intestinal magnesium handling.

The gene for human fibronectin glomerulopathy maps to 1q32, in the region of the regulation of complement activation gene cluster

Fibronectin glomerulopathy (GFND) is a newly recognized autosomal dominant disease of the kidney that results in albuminuria, microscopic hematuria, hypertension, renal tubular acidosis type IV, and end-stage renal disease in the 2d to 6th decade of life. The disease is characterized histologically by massive deposits of fibronectin (Fn) present in the subendothelial spaces of renal glomerular capillaries. The cause of human GFND is unknown. In order to localize a candidate gene for GFND, we performed linkage analysis of a large, 193-member pedigree containing 13 affected individuals. Since we had previously excluded the genes for Fn and uteroglobin as candidate genes for GFND, a total-genome search for linkage was performed. Examination of 306 microsatellite markers resulted in a maximum two-point LOD score of 4.17 at a recombination fraction of. 00 for marker D1S249, and a maximum multipoint LOD score of 4.41 for neighboring marker D1S2782. By detection of recombination events, a critical genetic interval of 4.1 cM was identified, which was flanked by markers D1S2872 and D1S2891. These findings confirm that GFND is a distinct disease entity among the fibrillary glomerulopathies. Gene identification will provide insights into the molecular interactions of Fn in GFND, as well as in genetically unaltered conditions.

Autosomal dominant medullary cystic kidney disease: evidence of gene locus heterogeneity

Autosomal dominant medullary cystic kidney disease (ADMCKD; synonym: medullary cystic disease, MCD) is an autosomal dominant kidney disorder, sharing morphological and clinical features with recessive juvenile nephronophthisis (NPH), such as reduced urinary concentration ability and multiple renal cysts at the corticomedullary junction. While in NPH end-stage renal disease (ESRD) occurs in adolescence, ADMCKD leads to ESRD in adulthood. Recently a gene locus for ADMCKD has been localized to chromosome 1q21 in two large Cypriot families. This prompted us to examine linkage in three ADMCKD-families, using the same set of polymorphic microsatellite markers spanning the critical region on chromosome 1q21. Haplotype analysis revealed that none of the three families showed linkage to this locus, thus demonstrating evidence for genetic locus heterogeneity. Additional linkage analysis studies need to be performed in order to identify further gene loci cosegregating with this autosomal dominant kidney disorder.