Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Q: Context: As of the 2010 United States Census, there were 1,951,269 people, 715,365 households, and 467,916 families residing in the county. The population density was . There were 840,343 housing units at an average density of . The racial makeup of the county was 60.9% white, 10.5% black or African American, 8.7% Asian, 0.7% Pacific islander, 0.7% American Indian, 13.5% from other races, and 5.1% from two or more races. Those of Hispanic or Latino origin made up 29.1% of the population. In terms of ancestry, 11.7% were Germans, 9.1% were Irish people, 7.6% were English people, 6.3% were Italians, and 2.7% were Americans. 
 Question: Which group from the census is larger: white or African American?

A: white
****
Q: Context: Mutations in the solute carrier family 9, subfamily A member 6 (SLC9A6) gene, encoding the endosomal Na+/H+ exchanger 6 (NHE6) are associated with Christianson syndrome, a syndromic form of X-linked intellectual disability characterized by microcephaly, severe global developmental delay, autistic behavior, early onset seizures and ataxia. In a 7-year-old boy with characteristic clinical and neuroimaging features of Christianson syndrome and epileptic encephalopathy with continuous spikes and waves during sleep, we identified a novel splice site mutation (IVS10-1G>A) in SLC9A6. These findings expand the clinical spectrum of the syndrome and indicate NHE6 dysfunction as a new cause of electrical status epilepticus during slow-wave sleep (ESES). 
 Question: Mutation of which gene is implicated in the Christianson syndrome?

A: slc9a6
****
Q: Context: Low back pain with or without radiculopathy is an important cause of disability and economic expenditure. However, many patients are not meeting optimal pain control through existing treatments. Recent studies have linked nerve growth factor (NGF) and the pathophysiology of persistent pain. Anti-NGF could be an alternative drug treatment for low back pain. Systematically review the efficacy and safety of anti-NGF in the treatment of low back pain. A systematic review of the literature with no language, date or publication status restriction, using Medline, EMBASE, Cochrane Library, and the clinicaltrials.gov database. Additional literature was retrieved by conferring with experts in the field or reviewing bibliographies and annals of meetings and congresses. Search terms included "monoclonal antibodies," "nerve growth factor," "anti-ngf," "fulranumab," "tanezumab," "sciatica," "back pain," and "spine." Inclusion criteria were observational studies with safety as an outcome and randomized or nonrandomized controlled trials studying the efficacy and/or the safety of anti-NGF drugs on low back pain. Exclusion criteria included patients with autoimmune conditions or osteoporosis. Studies were assessed independently by 2 authors regarding inclusion/exclusion criteria, risk of bias, clinical relevance, and quality of evidence (GRADE approach). 1,168 studies were retrieved. After excluding duplicates and applying the inclusion/exclusion criteria, 4 RCTs remained (n = 2,109): 2 for tanezumab, one for REGN475, and one for fulranumab. Only the tanezumab studies showed any significant difference over placebo (n = 1,563) for both pain relief and functional improvement. There is very low evidence that systemically administered anti-NGF therapy has a small positive effect compared to placebo for both pain relief (standarized mean difference [SMD] = -0.29, 95% confidence interval [CI] -0.58 to 0.00) and functional improvement (SMD = -0.21, 95%CI -0.37 to -0.05 ) of low back pain. There was low evidence of adverse effects (AEs) compared to placebo and low evidence of neurological AEs than placebo (relative risk = 1.93, 95%CI 1.41 to 2.64).Tanezumab, as a specific anti-NGF treatment, showed low evidence of a small to moderate effect for pain relief of low back pain (SMD = -0.44, 95%CI -0.81 to -0.07); and low evidence of a small effect for functional improvement (SMD = -0.26, 95%CI -0.40 to -0.12) with systemic administration, although not clinically significant. Tanezumab and anti-NGFs overall had, respectively, moderate and low evidence of overall AEs and serious AEs and a higher risk of developing neurological AEs when compared with placebo. Although anti-NGF, specifically tanezumab, showed a low-to-moderate effect on pain relief and functional improvement, it cannot be recommended for low back pain treatment. Without more research on the pathophysiology of anti-NGFs and adverse effects, its use is not safe in the overall population. However, as corroborated by the US Food and Drug Administration, this meta-analysis underscores a role for greater insight into anti-NGF therapy for painful conditions that are refractory to current drugs, such as oncologic pain, chronic pancreatitis, and phantom-limb pain. Given the pathophysiology of axial pain involving inflammatory mediators and the adverse effects of systemic anti-NGF use, consideration of local therapies may warrant further exploration. 
 Question: What is the target of tanezumab?

A:
ngf
****