Graft diameter does not influence primary stability of ulnar collateral ligament reconstruction of the elbow.

BACKGROUND: Ulnar collateral ligament insufficiency may result in medial elbow pain, instability, and reduced athletic performance in throwing athletes. Several reconstruction methods have been described, but biomechanical studies suggest that in general, stability of the graft construct is inferior to the native ulnar collateral ligament. This study investigates whether a stronger graft would yield greater resistance to valgus load over the range of motion. METHODS: Ten cadaveric elbows were mounted to a testing fixture and incremental valgus moments of 2.5, 5, and 7.5 Nm were applied with the elbow in 120°, 90°, 60°, 30° and 0° of flexion and in varying rotational forearm positions. The intact and the ulnar collateral ligament released elbow joint were compared with the docking ulnar collateral ligament reconstruction technique, using different graft sources with increasing cross-sectional areas: palmaris longus, tricpes brachii, extensor carpi radialis longus, and semitendinosus. The resulting angular displacement was evaluated and compared between graft sources and different elbow positions. RESULTS: Compared with the intact situation, ulnar collateral ligament release resulted in a significant increase in valgus deformation over the entire range of flexion-extension motion. Ligament reconstruction using any graft source significantly restored valgus stability at 60°, 90°, and 120°, while at 0° and 30°, angular valgus deformation did not significantly differ from the ulnar collateral ligament deficient situation. There were no significant differences in angular valgus deformation between the graft sources over the range of flexion motion or forearm rotation. CONCLUSIONS: This study did not prove that a thicker graft yielded more resistance to valgus moments when using the docking technique. Thicker grafts require larger bone tunnels, cannot be adequately tensioned, and are non-anatomic. Therefore, the palmaris longus or a triceps tendon strip are considered more appropriate for ulnar collateral ligament reconstruction.

Algorithm for efficient PKHD1 mutation screening in autosomal recessive polycystic kidney disease (ARPKD).

Autosomal recessive polycystic kidney disease (ARPKD) is an important cause of childhood renal- and liver-related morbidity and mortality with variable disease expression. While most cases manifest peri-/neonatally with a high mortality rate in the first month of life, others survive to adulthood. ARPKD is caused by mutations in the Polycystic Kidney and Hepatic Disease 1 (PKHD1) gene on chromosome 6p12. PKHD1 is an exceptionally large gene (470 kb) with a longest open reading frame transcript of 67 exons predicted to encode a 4,074-amino acid (aa) (447 kDa) multidomain integral membrane protein (fibrocystin/polyductin) of unknown function. Recent DHPLC-based mutational studies have reported detection rates of about 80% and a minimum of one PKHD1 mutation in more than 95% of families. Thus far, a total of 263 different PKHD1 mutations (639 mutated alleles) are included in the locus-specific database (www.humgen.rwth-aachen.de). Except for a few population-specific founder alleles and the common c.107C>T (p.Thr36Met) missense change, PKHD1 is characterized by significant allelic diversity, making mutation screening time-consuming and labor-intensive. Mutations are distributed throughout the gene's coding sequence; however, they are not equally scattered. Thus, we aimed to set up an algorithm for efficient molecular genetic diagnostics in ARPKD. A total of 80% of known PKHD1 mutations can be identified if a subset of 27 out of 77 DHPLC fragments is screened. The current study provides an essential platform for PKHD1 mutation screening in a routine setting that will largely alleviate molecular genetic diagnostics in patients suspected to have ARPKD.

PKHD1 mutations in families requesting prenatal diagnosis for autosomal recessive polycystic kidney disease (ARPKD).

Autosomal recessive polycystic kidney disease (ARPKD) is one of the most common hereditary renal cystic diseases in children. The clinical spectrum ranges from stillbirth and neonatal demise to survival into adulthood. In a given family, however, patients usually display comparable phenotypes. Many families who lost a child with severe ARPKD desire an early and reliable prenatal diagnosis (PD). Given the limitations of antenatal ultrasound, this is only feasible by molecular genetics that became possible in 1994 when PKHD1, the locus for ARPKD, was mapped to chromosome 6p. However, linkage analysis might prove difficult or even impossible in families with diagnostic doubts or in whom no DNA of an affected child is available. In such cases the recent identification of the PKHD1 gene provides the basis for direct mutation testing. However, due to the large size of the gene, lack of knowledge of the encoded protein's functional properties, and the complicated pattern of splicing, significant challenges are posed by PKHD1 mutation analysis. Thus, it is important to delineate the mutational spectrum and the reachable mutation detection rate among the cohort of severely affected ARPKD patients. In the present study, we performed PKHD1 mutation screening by DHPLC in a series of 40 apparently unrelated families with at least one peri- or neonatally deceased child. We observed 68 out of an expected 80 mutations, corresponding to a detection rate of 85%. Among the mutations identified, 23 were not reported previously. We disclosed two underlying mutations in 29 families and one in 10 cases. Thus, in all but one family (98 percent;), we were able to identify at least one mutation substantiating the diagnosis of ARPKD. Approximately two-thirds of the changes were predicted to truncate the protein. Missense mutations detected were nonconservative, with all but one of the affected amino acid residues found to be conserved in the murine ortholog. PKHD1 mutation analysis has proven to be an efficient and effective means to establish the diagnosis of ARPKD.

PKHD1 mutations in autosomal recessive polycystic kidney disease (ARPKD).

Autosomal recessive polycystic kidney disease (ARPKD) is an important cause of childhood renal- and liver-related morbidity and mortality. The clinical spectrum is widely variable. About 30 to 50% of affected individuals die in the neonatal period, while others survive into adulthood. ARPKD is caused by mutations in the PKHD1 (polycystic kidney and hepatic disease 1) gene on chromosome 6p12, which is among the largest human genes, with a minimum of 86 exons assembled into a variety of alternatively spliced transcripts. The longest continuous open reading frame is predicted to yield a 4,074-aa (447-kDa) multidomain integral membrane protein (fibrocystin/polyductin) of unknown function. This update compiles all known PKHD1 mutations and polymorphisms/sequence variants. Mutations were found to be scattered throughout the gene without evidence of clustering at specific sites. Most PKHD1 mutations are unique to single families ("private mutations") hampering genotype-phenotype correlations. Correlations have been drawn for the type of mutation rather than for the site of individual mutations. All patients carrying two truncating mutations displayed a severe phenotype with perinatal or neonatal demise, while patients surviving the neonatal period bear at least one missense mutation. However, some missense changes are obviously as devastating as truncating mutations. The present article intends 1) to provide an overview of PKHD1 mutations and polymorphisms/sequence variants identified so far, 2) to discuss potential genotype-phenotype correlations, and 3) to review them in the context of their clinical implications. A constantly updated list of mutations is available online (www.humgen.rwth-aachen.de) and investigators are invited to submit their novel data to this PKHD1 mutation database.

Functional analysis of PKHD1 splicing in autosomal recessive polycystic kidney disease.

Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in the PKHD1 (polycystic kidney and hepatic disease 1) gene on chromosome 6p12. The longest continuous open reading frame comprises 66 exons encoding a novel 4,074 aa multidomain integral membrane protein (polyductin/fibrocystin) of unknown function. Various alternatively spliced transcripts may additionally result in different isoproteins. Overall, the large size of PKHD1, its complex pattern of splicing, multiple allelism and lack of knowledge of the encoded protein's/proteins' functions pose significant challenges to DNA-based diagnostic testing. Nucleotide substitutions, particularly if residing in regulatory elements or introns outside the splice consensus sites, are often difficult to assess without further functional analyses and cannot be unambiguously classified as disease-associated. Investigations on the transcript level, however, are hampered as PKHD1 is not widely expressed in blood lymphocytes. We thus determined the functional significance of the novel splice site mutation c.53-3C>A in intron 2 by RNA analyses by minigene-construction. The mutant allele was shown to cause skipping of exon 3. Thus, given the minigene results together with 400 control chromosomes negative for this change, segregation of the mutation with the phenotype, and a significant lowering of the strength of the splice site by bioinformatics, the mutant allele is most likely pathogenic. To the best of our knowledge, this is the first study that defines the consequences of a PKHD1 splice mutation and underlines the relevance of functional analyses in determining the pathogenicity of changes of unknown significance.

Diagnosis, pathogenesis, and treatment prospects in cystic kidney disease.

Cystic kidney diseases (CKDs) are a clinically and genetically heterogeneous group of disorders characterized by progressive fibrocystic renal and hepatobiliary changes. Recent findings have proven the cystogenic process to be compatible with cellular dedifferentiation, i. e. increased apoptosis and proliferation rates, altered protein sorting and secretory characteristics, as well as disorganization of the extracellular matrix. Compelling evidence suggests that cilia play a central pathogenic role and most cystic kidney disorders converge into a common pathogenic pathway. Recently, several promising trials have further extended our understanding of the pathophysiology of CKD and may have the potential for rational personalized therapies in future years. This review aims to summarize the current state of knowledge of the structure and function of proteins underlying polycystic kidney disease, to explore the clinical consequences of changes in respective genes, and to discuss potential therapeutic approaches.

Clinical consequences of PKHD1 mutations in 164 patients with autosomal-recessive polycystic kidney disease (ARPKD).

BACKGROUND: ARPKD is associated with mutations in the PKHD1 gene on chromosome 6p12. Most cases manifest peri-/neonatally with a high mortality rate in the first month of life while the clinical spectrum of surviving patients is much more variable than generally perceived. METHODS: We examined the clinical course of 164 neonatal survivors (126 unrelated families) over a mean observation period of 6 years (range 0 to 35 years). PKHD1 mutation screening was done by denaturing high-performance liquid chromatography (DHPLC) for the 66 exons encoding the 4074 aa fibrocystin/polyductin protein. RESULTS AND CONCLUSION: This is the first study that reports the long-term outcome of ARPKD patients with defined PKHD1 mutations. The 1- and 10-year survival rates were 85% and 82%, respectively. Chronic renal failure was first detected at a mean age of 4 years. Actuarial renal survival rates [end point defined as start of dialysis/renal transplantation (RTX) or by death due to end-stage renal disease (ESRD)] were 86% at 5 years, 71% at 10 years, and 42% at 20 years. All but six patients (92%) had a kidney length above or on the 97th centile for age. About 75% of the study population developed systemic hypertension. Sequelae of congenital hepatic fibrosis and portal hypertension developed in 44% of patients and were related with age. Positive correlations could further be demonstrated between renal and hepatobiliary-related morbidity suggesting uniform disease progression rather than organ-specific patterns. PKHD1 mutation analysis revealed 193 mutations (70 novel ones; 77% nonconservative missense mutations). No patient carried two truncating mutations corroborating that one missense mutation is indispensable for survival of newborns. We attempted to set up genotype-phenotype correlations and to categorize missense mutations. In 96% of families we identified at least one mutated PKHD1 allele (overall detection rate 76.6%) indicating that PKHD1 mutation screening is a powerful diagnostic tool in patients suspected with ARPKD.